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THE 

CHEMISTRY 

OF 

PAINTS  AND  PAINT 
VEHICLES 


BY 

CLARE  H.  HALL,  B.S. 

Chemist  for  The  Chas.  Moser  Co. 


NEW  YORK 

D.  VAN    NOSTRAND    COMPANY 

23  MURRAY  AND  27  WARREN  STREETS 
1906 


Copyright  1906 
BY  D.  VAN  NOSTRAND  Co. 


The  Plimpton  Press  Norwood  Mass.  U.S.  A, 


CONTENTS 

CHAPTER  PAGE 

I  THE  DETERMINATION  OF  THE  ELEMENTARY 

CONSTITUENTS  OF  PAINTS    .      .      .      .     ;         i 
II  RAW  MATERIALS,  PROPERTIES,  TESTS,  AND 

METHODS  OF  ANALYSIS 15 

III  THE  ANALYSIS   OF   DRY    COLORS,   PASTES, 

AND  LIQUID  PAINTS 46 

IV  THE  MATCHING  OF  SAMPLES 67 

V  PAINT  VEHICLES 76 

APPENDIX 115 


331000 


PREFACE 

IN  writing  this  book  the  author  has  attempted 
to  sift  from  the  great  mass  of  analytical  chemistry 
those  methods  which  apply  particularly  to  the 
analysis  of  paints,  at  the  same  time  calling  atten- 
tion to  the  most  important  physical  characteristics 
of  the  raw  materials.  No  chemist  can  be  pro- 
ficient in  the  analysis  of  paints  without  a  thorough 
knowledge  of  all  the  materials  with  which  he  comes 
in  contact,  and  although  no  attempt  is  here  made 
to  give  anything  more  than  the  most  general  facts 
regarding  them  it  is  to  be  hoped  that  such  will 
be  sufficient  to  act  as  an  incentive  for  each  to 
personally  investigate  all  pigments,  etc.,  until 
thoroughly  familiar  with  their  every  aspect. 

The  general  scheme  which  the  author  has  at- 
tempted to  follow  is  to  take  up  in  Chapter  I  the 
elementary  constituents  of  paints  with  the  quanti- 
tative methods  for  their  determination;  in  Chapter 
II  the  dry  materials  entering  into  the  manufacture 
of  paints  with  a  short  description  of  their  physical 
properties  and  the  separation  of  their  elementary 
constituents  by  methods  given  in  Chapter  I;  in 
Chapter  III  the  analysis  of  samples  consisting  of 
a  mixture  of  two  or  more  of  the  raw  materials 
described  in  Chapter  II;  in  Chapter  IV  an  inter- 
pretation of  results  previously  obtained  where  it 


vi  PREFACE 

is  desired  to  duplicate  the  sample  analyzed;  and 
finally,  in  Chapter  V,  descriptions  and  methods 
for  determining  the  purity  of  paint  vehicles. 

The  close  connection  between  the  facts  treated 
in  the  first  three  chapters  has  made  it  impossible 
to  separate  them  by  very  definite  lines  of  demarca- 
tion. This  necessitates  their  overlapping,  especially 
in  the  case  of  Chapters  II  and  III. 

This  book  being  written  from  the  standpoint 
of  a  chemist  employed  in  the  manufacture  of  paints 
and  colors,  Chapter  IV  has  been  included  in  an 
attempt  to  bridge  the  space  between  the  laboratory 
and  factory.  It  is  here  that  so  often  the  results 
of  previous  analysis  are  rendered  worthless  by 
being  placed  in  the  hands  of  one  who  does  not 
understand  their  interpretation  nor  the  composi- 
tion of  the  raw  materials  which  he  is  using.  Over 
this  work  the  chemist  should  have  final  super- 
vision. 


CHAPTER  I 

THE  DETERMINATION  OF  THE  ELEMENTARY 
CONSTITUENTS  OF  PAINTS 

ALUMINIUM 

A.  I.    Determination  as  Oxide.  —  If  NH4C1  is  not 

already  present,  add  it  to  the  solution  in  moderate 
quantities,  then  NH4OH  in  slight  excess.  Boil 
until  no  odor  of  ammonia  is  perceptible.  Let  settle, 
decant  the  supernatant  liquid  onto  filter  and  re- 
peat several  times.  Finally  wash  the  precipitate 
on  filter  until  free  from  chlorides;  dry,  ignite,  and 
weigh  as  A12O3. 

A.  II.  Separation  of  Aluminium  from  Iron.  — 
Precipitate  with  NH4OH  as  in  A.  I.  Wash,  filter, 
dry,  ignite,  and  weigh  combined  oxides.  Now  fuse 
with  KOH  in  a  silver  crucible  in  order  to  dissolve 
the  A12O3.  Digest  fused  mass  in  water  and  wash 
the  residue  of  Fe2O3.  Dissolve  in  HC1,  and  re- 
precipitate  with  NH4OH,  in  order  to  free  the  iron 
from  potassium  salts,  then  dry,  ignite,  weigh,  and 
get  A12O3  by  difference. 

BARIUM 

B.  I.    Determination  as  Sulphate. — Heat  the  solu- 
tion, which  should  not  contain  too  much  free  acid, 

i 


2  THE  CHEMISTRY  OF  PAINTS 

then  add  excess  of  hot  dilute  H2SO4,  and  keep  the 
mixture  near  the  boiling  point  for  some  time.  De- 
cant supernatant  liquid  onto  Gooch  crucible,  and 
boil  the  precipitate  with  water.  Finally  transfer 
and  wash  on  Gooch  crucible  with  hot  water  until 
nitrate  shows  no  turbidity  with  BaCl2.  Dry,  ignite, 
and  weigh  as  BaSO4. 
Separation  from  Calcium.  —  See  C.  II. 

CALCIUM 

C.  I.  Determination  as  Oxide.  —  To  the  boiling 
solution  made  alkaline  with  NH4OH,  add  an  excess 
of  boiling  ammonium  oxalate.  Boil  or  keep  near 
boiling-point  for  some  time,  then  let  settle,  filter, 
and  wash  with  boiling  water  until  free  from  am- 
monium salts.  Dry,  transfer  to  platinum  crucible, 
and  ignite  over  blast  lamp  for  fifteen  minutes; 
weigh,  and  again  ignite  for  five  minutes.  If  there 
is  any  change  in  weight,  ignite  again  to  constant 
weight.  Where  the  quantity  of  calcium  is  small 
one  ignition  will  usually  suffice.  Weigh  as  CaO. 

C.  II.  Separation  from  Barium.  —  Precipitate 
combined  calcium  and  barium  with  ammonia  and 
ammonium  carbonate.  Filter  on  a  Gooch  crucible, 
dry  and  ignite  at  a  very  gentle  heat,  adding  a  small 
amount  of  ammonium  carbonate  to  convert  any 
CaO  to  CaCO3.  Weigh  the  combined  carbonates; 
dissolve  in  HC1,  filter  out  asbestos,  dilute  highly, 
boil,  and  precipitate  barium  with  a  very  dilute 


CONSTITUENTS  OF  PAINTS  3 

solution  of  hot  H2SO4.  Decant  on  filter,  wash  with 
hot  water  and  HC1  to  dissolve  any  traces  of  calcium 
sulphate  that  may  have  precipitated,  and  determine 
barium  as  in  B.  I.  Calculate  BaSO4  to  BaCO3, 
and  get  CaCO3  by  difference. 

CARBON 
C.  III.     Determination  of  Carbon  Dioxide. 


APPARATUS.  —  A  is  a  bottle  containing  potash 
which  serves  to  prevent  any  CO2  from  the  air  enter- 
ing the  apparatus,  and  through  it  air  is  drawn  into 
the  flask  B,  in  which  the  carbonates  are  decomposed. 
B  contains  a  stoppered  funnel  tube  G,  and  is  con- 
nected with  the  calcium  chloride  tube  C,  which 
serves  to  prevent  moisture  from  entering  the  potash 
bulbs  D.  E  is  another  calcium  chloride  tube  and 
is  connected  with  the  aspirator  at  F. 

PROCESS.  —  Place  weighed  sample  (5  gms.)  in 
flask  B.  Now  carefully  weigh  the  potash  bulbs 
(they  should  be  stoppered  with  short  pieces  of  glass 
rod),  and  then  connect  the  apparatus  as  shown 
above.  Add  water  to  the  flask  B  through  G,  and 
draw  a  current  of  air,  about  one  bubble  per  second, 
through  the  apparatus.  Next  add  acid  slowly 


4  THE  CHEMISTRY  OF  PAINTS 

through  G,  closing  the  cock  after  each  addition, 
meanwhile  heating  the  flask  gently,  and  slowly  in- 
creasing flow  of  air.  When  no  more  action  is 
produced  by  the  further  addition  of  acid,  remove 
all  CO2  from  the  apparatus  by  suction,  then  re- 
move potash  bulbs,  restopper  them  with  stoppers 
formerly  used,  and  after  thirty  minutes  weigh  and 
get  CO2  by  increase  in  weight. 

CHROMIUM 
C.  IV.     Determination  as  Chromic  Oxide. —  All 

chromate  compounds  must  first  be  changed  into 
the  chromic  state,  which  is  indicated  by  an  intense 
green  color,  without  any  red  or  yellow.  If  not 
already  in  this  condition  add  a  small  amount  of 
HC1  and  boil  until  the  change  is  complete.  Add 
NH4OH  in  slight  excess  and  boil  until  supernatant 
liquid  is  colorless;  then  wash  precipitate  (Cr2(OH)6) 
by  decantation  several  times  and  transfer  to  filter, 
dry,  ignite,  and  weigh  as  Cr2O3.  If  filtrate  is  yellow 
it  indicates  that  the  chromate  has  not  been 
completely  reduced. 

Separation  from  Iron  and  Mn.  —  See  I.  II.  and 
M.  III. 

C.  V.  Chromates  Soluble  in  Water.  —  When  a 
chromate  compound  soluble  in  water  is  digested 
with  HC1  the  following  reaction  takes  place :  — 

K2Cr2O7  +  I4HC1  =  2KC1  +  Cr2Cl6  +  7H2O  +  6C1. 

If  potassium  iodide  is  present  each  atom  of  free 
Cl  will  replace  an  equivalent  of  I,  and  the  liberated 


CONSTITUENTS  OF  PAINTS  5 

iodine  may  be  titrated  with  a  standard  solution  of 
sodium  thio-sulphate  (Na2S2O3).  The  application 
of  these  reactions  to  the  determination  of  chromium 
is  as  follows:  Place  a  weighed  quantity  of  the 
chromate  in  a  flask  with  water  and  an  excess  of  po- 
tassium iodide.  When  dissolved  add  an  excess  of 
HC1,  then  cork  the  flask  tightly  and  allow  the 
mixture  to  digest  at  gentle  heat  for  some  time,  cool, 
uncork,  wash  into  a  beaker  and  titrate  with  standard 
sodium  thio-sulphate,  using  starch  solution  as  an 
indicator. 

The  n/io  sodium  thio-sulphate  solution  may  be 
made  as  follows:  Dissolve  24.822  gms.  of  c.p. 
transparent  crystals  in  one  liter  of  distilled  water 
at  15.5°  C.  This  is  best  checked  by  standardizing 
against  n/io  K2Cr2O7  made  by  dissolving  4.913 
gms.  c.p.  K2Cr2O7  in  one  liter  of  distilled  water 
at  15. 5°  C.;  25  c.c.  K2Cr2O7  are  treated  as  above 
with  KI  and  HC1.  The  I  liberated  is  titrated  with 
the  Na2S2O3  solution,  using  starch  solution  as  an 
indicator.  When  the  Na2S2O3  solution  is  added 
in  sufficient  quantities  to  take  up  all  free  iodine 
present  the  blue  color  caused  by  free  iodine  in  the 
presence  of  starch  will  disappear.  The  green  color 
due  to  chromic  salts  must  not  be  confused  with  the 
blue.  A  very  little  practice  will  enable  the  operator 
to  distinguish  between  them.  The  strength  of 
the  thio-sulphate  solution  may  now  be  calculated, 
remembering  that  each  atom  of  free  Cl  in  above 
equation  releases  one  atom  of  I.  It  will  be  found 


6  THE  CHEMISTRY  OF  PAINTS 

more  convenient  to  express  results  as  i  c.c.  Na2S2O3 
=  x  gms.  K2Cr2O7  and  i  c.c.  Na2S2O3=x  gms.  I. 

The  first  equation  is  used  to  calculate  the  strength 
of  all  chromate  solutions,  while  the  second  is  used  in 
calculating  free  iodine,  as  in  the  iodine  absorption 
method. 

As  the  Na2S2O3  solution  changes  on  standing  it 
should  be  restandardized  with  n/io  K2Cr2O7  at  fre- 
quent intervals.  The  change  will  be  greatly  or  wholly 
reduced  by  keeping  in  a  dark  place  and  protecting 
from  the  air  by  means  of  a  layer  of  kerosene. 

If  insoluble  chromates,  such  as  PbCrO4  are  to  be 
determined,  this  process  must  be  slightly  varied 
as  boiling  with  HC1  is  necessary  to  effect  complete 
decomposition.  In  such  cases  proceed  as  in  the 
determination  of  MnO2  by  the  Bunsen  Method. 
(See  M.  IV.) 

C.  V.  a.  Chromates  Soluble  in  Water.  —  Such  as 
Na2Cr2O7  and  K2Cr2O7  are  readily  analyzed  by 
dissolving  in  water,  adding  a  small  amount  of 
dilute  HNO3,  and  precipitating  with  lead  nitrate 
or  acetate.  The  PbCrO4  thus  formed  is  washed, 
filtered  on  a  Gooch  crucible,  and  dried  at  a  low 
temperature  to  constant  weight.  From  the  weight 
of  the  PbCrO4  present  the  per  cent  Cr2O3  or 
Na2Cr2O7  may  be  readily  calculated. 

IRON 

I.  I.  Determination  as  Ferric  Oxide.  — Oxidize 
any  ferrous  iron  to  ferric,  precipitate  with  NH4OH 


CONSTITUENTS  OF    PAINTS  7 

in  excess,  boil,  filter,  wash,  dry,  ignite  filter  and 
precipitate  separately,  and  weigh  as  Fe2O3. 

I.  II.  Separation  from  Chromium.  —  Proceed  as 
directed  in  I.  I.  Fuse  the  weighed  oxides  with  two 
parts  KNO3  and  four  parts  Na2CO3  in  a  platinum 
crucible.  Treat  the  mass  with  boiling  water  in  a 
beaker,  adding  a  small  quantity  of  alcohol  and  heat 
gently  for  several  hours.  Filter.  The  filtrate  will 
contain  all  the  chromate  as  alkali  chromate,  while 
the  iron  will  remain  as  a  residue  on  the  filter.  Wash 
the  residue  thoroughly,  dissolve  in  HC1,  reprecipitate 
with  NH4OH,  filter,  then  dry,  ignite,  and  weigh  as 
Fe20, 

Make  the  chromate  solution  acid  with  HC1,  add 
more  alcohol,  boil  to  reduce  chromic  acids  to 
chromic  salts,  and  treat  as  in  C.  IV. 

I.  III.  Determination  with  Potassium  Perman- 
ganate. —  The  following  method  gives  very  rapid, 
accurate  results  but  is  used  to  advantage  only  when 
a  number  of  iron  determinations  are  to  be  made. 

PERMANGANATE  SOLUTION.  —  Weigh  out  3.162 
gms.  c.p.  KMnO4  and  dissolve  in  one  liter  distilled 
water  at  15.5°  C.  Check  the  solution  with  n/io 
oxalic  acid  solutions  as  follows:  25  c.c.  n/io 
oxalic  acid  are  heated  to  60°  with  H2SO4  present 
and  the  KMnO4  solution  added  to  faint  permanent 
pink.  From  this  the  strength  of  the  KMnO4  solu- 
tion is  calculated  and  will  generally  be  found  the 
same  as  that  calculated  from  the  weight.  The 
reaction  that  takes  place  is  as  follows:  — 


8  THE  CHEMISTRY  OF  PAINTS 

Mn2O7 + 5H2C204  +  2H2SO4 = 
ioCO2+2MnSO4  +  7H2O 

Another  method  of  standardizing  the  KMnO4 
solution  is  to  titrate  it  against  pure  iron  wire  and 
thus  find  the  equivalent  of  i  c.c.  in  grams  iron.  To 
do  this  fit  a  rubber  stopper  with  a  bent  delivery 
tube  into  a  flask  holding  about  30  c.c.  Clamp 
into  a  retort  stand  in  an  inclined  position,  having 
the  tube  so  bent  as  to  dip  into  a  small  beaker  con- 
taining water.  Fill  the  flask  one  third  full  with 
dilute  H2SO4,  add  a  little  Na2CO3  and  when  the 
CO2  gas  evolved  has  driven  out  all  the  air,  add  o.i 
gm.  pure  iron  wire  to  the  contents  of  the  flask  and 
heat  gently  until  dissolved.  Then  cool  rapidly  under 
a  stream  of  water  and  add  KMnO4  solution  to 
faint,  permanent  pink.  Express  results  as  i  c.c. 
KMnO4=x  gms.  metallic  iron. 

To  determine  iron  in  any  compound  dissolve  in 
HC1,  reduce  with  metallic  zinc  in  a  flask  or  better 
by  passing  through  a  Johnes  Reductor.  Add 
H2SO4  and  titrate  with  standard  KMnO4  solution 
as  above. 

It  will  be  seen  that  this  method  also  offers  a  very 
ready  means  for  separating  ferrous  from  ferric  iron. 
After  the  total  iron  has  been  determined  the  ferrous 
iron  is  determined  by  dissolving  without  oxidation 
as  with  iron  wire  and  determining  the  amount 
by  titration  with  the  KMnO4  solution  to  faint,  per- 
manent pink.  The  difference  between  the  amount 
of  ferrous  iron  thus  determined  and  the  total 


CONSTITUENTS  OF  PAINTS  9 

amount  found  will  be  the  amount  of  ferric  iron 
present. 

Potassium  permanganate  solutions  may  be  ren- 
dered stable  by  filtering,  through  asbestos  after 
preparation.  Still  more  satisfactory  results  may 
be  obtained  by  warming  and  allowing  to  stand  two 
days  before  decanting  and  filtering.  In  case  this  is 
not  done  an  unstable  solution  will  result  which 
must  be  restandardized  whenever  used  if  satis- 
factory results  are  to  be  obtained. 

LEAD 

L.  I.  Determination  as  Sulphate.  —  To  the  solu- 
tion add  H2SO4  in  slight  excess,  and  if  HC1  or 
HNO3  is  present  evaporate  to  sulphuric  acid  fumes. 
Dilute  highly  with  water  and  an  equal  volume  of 
alcohol,  filter  on  a  Gooch  crucible,  wash  with  a 
hot  mixture  of  equal  parts  water  and  alcohol,  dry, 
ignite,  and  weigh  as  PbSO4. 

MAGNESIUM 

M.  I.  Determination  as  Magnesium  Pyrophos- 
phate.  —  Make  the  solution  alkaline  with  NH4OH 
and  if  any  precipitate  forms  add  NH4C1  until  it 
is  dissolved.  Add  sodium  acid  phosphate  in  excess, 
and  stir  the  mixture,  taking  care  not  to  touch  the 
sides  of  the  beaker  with  the  stirring  rod.  Cover 
the  beaker,  and  allow  it  to  stand  in  a  cool  place  for 
at  least  twelve  hours,  after  which  filter  and  rinse 
out  the  beaker  with  a  portion  of  the  filtrate.  Now 


10          THE  CHEMISTRY  OF  PAINTS 

wash  precipitate  with  a  mixture  of  three  parts 
water,  and  one  part  ammonia  water  until  the  filtrate 
is  free  from  sodium  salts.  Dry,  and  separate  from 
the  filter  paper.  Transfer  the  bulk  of  precipitate 
to  a  platinum  crucible,  burning  the  paper  separately 
on  platinum  wire,  and  later  adding  the  residue  to 
the  contents  of  the  crucible.  Put  on  the  lid  and  ex- 
pose for  sometime  to  gentle  heat,  gradually  increas- 
ing to  intense  redness.  Cool,  and  weigh  as  Mg2P2O7. 

MANGANESE 

M.  II.  Determination  as  Mn304.  —  Precipitate 
the  solution,  which  should  not  be  too  concentrated, 
with  NaOH  or  KOH.  Boil,  transfer  precipitate 
to  the  filter  and  wash  until  free  from  alkali.  Dry, 
separate  from  filter  paper  and  burn  paper  separately 
as  described  above.  Heat  to  constant  weight  and 
weigh  as  Mn3O4. 

M.  III.  Separation  from  Iron.  —  Treat  com- 
bined iron  and  manganese  as  in  M.  II.,  and  weigh 
the  combined  oxides,  then  fuse  with  Na2CO3,  dis- 
solve the  mass  in  HNO3  and  then  boil,  adding  now 
and  then  KC1O3  crystals.  The  bioxide  of  man- 
ganese is  formed  and  being  insoluble  in  strong 
HNO3  separates  as  a  precipitate.  When  fumes 
cease  with  a  slight  explosion  the  manganese  has 
been  completely  oxidized.  Add  a  few  more  crystals 
of  KC1O3,  boil,  filter  on  a  Gooch  crucible  and  wash 
with  strong  HNO3.  Transfer  contents  of  crucible 
to  a  bqaker  and  digest  in  HC1.  Filter  out  the 


CONSTITUENTS  OF  PAINTS 


II 


asbestos,  nearly  neutralize  with  NH4OH,  then  add 
some  sodium  acetate  to  precipitate  any  remaining 
traces  of  iron.  Boil  and  filter.  Heat  the  solution 
nearly  to  boiling  and  add  an  excess  of  microcosmic 
salt.  Now  make  slightly  alkaline  with  NH4OH, 
boil,  stirring  until  precipitate  assumes  the  charac- 
teristic appearance  of  ammonium  manganese  phos- 
phate. Treat  the  precipitate  as  in  M.  L,  weighing 
as  pyrophosphate  (Mn2P2O7).  This  method  also 
can  be  applied  to  the  separation  of  manganese 
from  chromium  and  other  metals  of  the  third  group. 
M.  IV.  Determination  of  Manganese  Dioxide, 
Bunsen's  Method.  —  Place  0.4  gm.  of  the  finely  pul- 


verized sample  in  the  flask  A,  and  pour  over  it  con- 
centrated HC1.  At  once  connect  A  to  B,  in  which 
is  a  solution  of  KI,  the  containing  tubes  being 
kept  cool  by  filling  the  beaker  about  one  half  full 
of  water.  Now  apply  a  burner  to  A  and  heat 
the  solution  until  the  sample  is  completely  dissolved 
and  all  the  evolved  chlorine  has  been  expelled  and 


12  THE  CHEMISTRY  OF  PAINTS 

driven  into  B.  This  requires  but  a  few  minutes. 
In  order  to  prevent  the  iodine  solution  from  being 
sucked  back  into  the  flask  A,  B  is  disconnected 
before  the  flame  is  removed  from  A.  Titrate  the 
free  iodine  in  B  with  standard  Na2S2O3  as  in  C.  V. 
From  this  calculate  the  amount  of  O  released,  and 
in  turn  the  amount  of  MnO2  present  in  sample. 
This  method  is  also  applicable  to  the  determination 
of  chromates  insoluble  in  water,  and  to  the  deter- 
mination of  PbO2  in  red  lead  and  orange  mineral. 

SILICON 

S.  I.  Silica  and  Silicates.  Decomposition  with 
Hydrofluoric  Acid.  —  The  purity  of  silica  may  be 
readily  tested  by  adding  to  the  finely  pulverized 
sample  in  a  platinum  crucible,  concentrated  hydro- 
fluoric acid,  then  evaporating  to  dryness  at  gentle 
heat  and  finally  igniting  to  intense  red  heat.  When 
the  sample  is  pure  silica  no  residue  will  be  left  after 
ignition. 

In  the  analysis  of  silicates  the  above  process  is 
varied  somewhat.  Proceed  in  the  same  manner, 
using,  however,  a  platinum  evaporating  dish  instead 
of  a  crucible,  and  before  the  HF  has  entirely 
evaporated,  let  cool,  and  add,  very  slowly,  concen- 
trated H2SO4  in  sufficient  quantities  to  convert  all 
bases  present  into  sulphates.  Evaporate  at  a  low 
temperature  to  sulphuric  acid  fumes.  Let  cool, 
and  dilute  with  water.  If  the  operation  has  been 
conducted  properly  there  should  be  no  residue 


CONSTITUENTS  OF  PAINTS  13 

unless  barytes  is  present,  and  in  that  case  it  will 
precipitate  at  once  after  diluting  the  concentrated 
H2SO4.  If  it  is  found  present  filter  on  a  Gooch 
crucible,  dry,  ignite,  and  weigh  as  BaSO4.  The 
bases  present  will  now  be  in  solution  as  sulphates. 
Add  NH4C1,  then  NH4OH  until  alkaline,  and  treat 
any  precipitate  of  aluminium  as  in  A.  I.  If  any 
iron  is  present  (as  in  ochres)  it  may  be  separated 
from  aluminium  by  A.  II  or  I.  III.  To  the  filtrate 
add  ammonium  oxalate  in  excess,  and  if  a  precipi- 
tate forms,  treat  as  in  C.  I.  Test  the  filtrate  for 
magnesium  by  M.  I,  and  if  found  present  determine 
accordingly.  Finally  obtain  the  quantity  of  SiO2 
present  by  difference  after  all  other  constituents 
including  water  have  been  determined.  This  method 
is  applicable  at  all  times  to  the  analysis  of  silicates 
entering  into  the  manufacture  of  paint,  and  offers 
a  much  better  method  for  separation  of  silicates 
from  barytes  than  does  the  method  of  fusing  with 
Na2C03. 

S.  I.  a.  Decomposition  with  Sodium  Carbonate  in 
absence  of  Barytes.  —  The  following  method  is 
recommended  for  analysis  of  silicates  where  separa- 
tion from  barytes  is  not  required  since  it  gives  SiO2 
direct,  and  not  by  difference. 

Fuse  a  weighed  quantity  of  the  silicate  with  five 
or  six  times  its  weight  of  Na2CO3  in  a  platinum 
crucible  over  a  blast  lamp.  When  cool,  dissolve 
the  mass  in  an  excess  of  HC1,  evaporate  nearly  to 
dryness  on  a  hot  plate,  then  in  drying-oven  at  1 10°  C. 


14  THE  CHEMISTRY  OF  PAINTS 

for  one  hour.  Add  dilute  HC1,  warm,  and  decant 
the  acid  onto  a  filter.  Again  add  acid  and  decant, 
and  finally  transfer  the  insoluble  residue  to  the 
filter,  and  wash  until  free  from  alkali  salts.  Dry, 
ignite,  and  weigh  as  SiO2.  Examine  the  filtrate  in 
the  same  manner  as  in  S.  I.  for  aluminium,  iron,  etc. 

SULPHUR 

S.  II.  Sulphates.  Determination  as  Barium  Sul- 
phate. —  Add  to  the  boiling  solution,  which  must 
not  contain  too  much  free  acid  (the  presence  of 
HNO3  especially  should  be  avoided),  an  excess  of 
boiling  barium  chloride  solution.  Keep  near  boiling 
for  some  time,  let  settle,  and  decant  the  supernatant 
liquid  onto  a  weighed  Gooch  crucible.  Wash  by 
decantation  with  boiling  water,  then  transfer  to  the 
crucible,  and  wash  until  the  last  washings  show  no 
traces  of  chlorides  with  silver  nitrate.  Dry,  ignite, 
and  weigh  as  BaSO4. 

ZINC 

Z.  I.  Determination  as  Oxide.  —  Heat  the  mod- 
erately dilute  solution,  which  must  contain  no 
ammonium  salts,  nearly  to  boiling  in  a  large  beaker, 
and  add  Na2CO3  in  excess.  Boil,  stirring  occa- 
sionally, to  avoid  bumping.  Allow  the  precipitate 
to  settle,  wash  thoroughly  by  decantation  onto  a 
filter  paper,  repeat  until  the  last  washings  are  free 
from  sodium  salts.  Dry  and  ignite  the  precipitate 
and  filter  paper  together,  and  weigh  as  ZnO. 


CHAPTER  II 

RAW    MATERIALS,    PROPERTIES,    TESTS, 
AND    METHODS  OF  ANALYSIS 

The  importance  of  the  strength  test  in  testing 
raw  materials  cannot  be  too  strongly  emphasized. 
All  raw  materials  used  should  be  analyzed,  an  OK 
sample  kept,  and  the  future  shipments  checked 
by  the  shade  in  oil,  and  by  a  strength  test.  This 
plan  will  be  found  much  simpler  and  more  satis- 
factory than  an  analysis,  but  it  of  course  does  not 
apply  to  whiting,  barytes,  and  similar  materials, 
which  are  used  only  as  adulterants  and  have  little 
body. 

Strength  Test.  —  Weigh  out  equal  portions  of 
the  color  to  be  tested,  and  the  OK  sample,  and  to 
each  add  equal  portions  of  zinc  oxide.  Transfer 
each  to  a  glass  plate  and  rub  with  a  spatula  until 
well  mixed.  Now  take  a  small  portion,  first  of  one 
then  of  the  other,  and  rub  on  ground  glass  until 
there  is  no  change  in  shade  on  further  rubbing. 
(In  the  case  of  Prussian  and  Chinese  blues,  greens, 
and  blacks,  the  mixture  must  be  rubbed  very  hard 
for  some  time.)  If  the  two  shades  are  the  same 
the  sample  is  of  proper  strength. 

Whites  may  be  tested  in  a  like  manner  by  com- 
paring the  shade  of  the  sample  and  the  OK  sample 

15 


16  THE  CHEMISTRY  OF  PAINTS 

in  bleached  oil,  and  by  adding  to  equal  portions  of 
each  equal  portions  of  some  color  and  treating  as 
above.  If  the  resulting  tints  are  alike  the  sample 
is  correct. 

The  relative  value  of  a  dry  color  may  also  be 
obtained  by  making  a  strength  test  between  it  and 
a  sample  of  known  purity,  which  has  the  same 
shade  in  oil  and  is  made  from  the  same  materials. 
To  do  this  weigh  out  equal  portions  of  the  known 
and  unknown  color  (the  amount  will  vary  with  the 
color  and  its  purity;  Chinese  and  Prussian  blue  and 
blacks  about  0.2  gms.,  other  colors  much  more,  up  to 
i  gm.,  may  be  taken).  Transfer  each  to  a  glass  plate. 
Now  weigh  out  two  portions  of  5  gms.  each  of  zinc 
oxide,  and  add  to  the  colors  on  the  glass.  Mix  as 
described  above  and  compare  the  shades  on  glass. 
If  they  are  the  same  their  value  is  the  same,  but  if 
one  is  darker  than  the  other  add  weighed  quantities 
of  the  zinc  oxide  until  the  shades  are  the  same 
after  rubbing  out  thoroughly.  The  percentage  dif- 
ference in  strength  and  value  may  now  be  deter- 
mined. For  instance:  Color  No.  i,  to  which  5  gms. 
of  zinc  oxide  is  added,  gives  the  same  shade  as  color 
No.  2  with  7  gms.  of  zinc  oxide  added.  Then  color 
No.  i  is  only  fy  as  strong  as  color  No.  2,  and  has 
only  f  of  its  value  plus  value  of  adulteration  present. 

BLUE  PIGMENTS 

Chinese  Blue.  —  This  pigment  is  made  by  pre- 
cipitating a  solution  of  yellow  prussiate  of  potash 


RAW  MATERIALS  17 

with  copperas  and  then  adding  some  oxidizing 
agent  to  convert  the  ferro-ferro-cyanide  thus  formed 
to  the  ferri-ferro-cyanide.  It  is  a  bulky  pigment, 
very  dark  blue  in  shade  with  a  decided  bronze 
cast,  but  having  a  beautiful  blue  tint.  The  color 
is  immediately-  destroyed  by  heat  and  fixed  alkali, 
but  is  unaffected  by  acids.  On  the  addition  of 
alkali  it  breaks  up  into  ferric  hydrate  and  an  alkali 
ferro-cyanide.  On  the  addition  of  acid  the  color 
reappears. 

Prussian  Blue.  —  Prussian  blue  is  very  dark  in 
color,  with  an  intense  blue  shade  in  oil,  and  without 
the  bronze  cast  of  the  Chinese  blue.  It  is  not  as 
strong  as  the  Chinese  blue,  and  the  tint  is  much  in- 
ferior. It  may  be  made  from  yellow  prussiate  of 
soda  and  in  consequence  costs  less  than  Chinese  blue. 

These  blues  are  very  seldom  adulterated  dry, 
but  when  this  is  done,  china  clay,  barytes,  starch 
etc.,  are  used.  To  test  for  starch,  boil  a  sample 
with  water,  let  settle,  filter,  and  add  a  potassium 
iodide  solution  of  iodine.  The  formation  of  a 
blue  color  is  evidence  of  starch.  For  the  deter- 
mination of  china  clay  and  barytes,  see  Dry  Colors, 
Chapter  III. 

It  will  always  be  found  much  more  convenient  to 
test  blues  by  strength  against  pure  samples  of  Prus- 
sian and  Chinese  blues  than  to  attempt  an  analysis. 

Ultramarine.  —  This  pigment  is  a  very  perma- 
nent blue,  much  lighter  in  shade  than  either  Prus- 
sian or  Chinese  blue,  and  of  a  much  more  brilliant 


l8  THE  CHEMISTRY  OF  PAINTS 

purple  tint.  It  has  about  the  same  value  as  a  tint- 
ing color,  but  cannot  safely  be  used  with  lead  com- 
pounds since  it  contains  sulphur,  and  hence  is 
likely  to  form  the  black  lead  sulphide.  It  is  found 
in  nature  as  the  mineral  lapis  lazuli,  but  at  the  pres- 
ent time  the  artificial  ultramarine  made  by  heating 
together  in  a  closed  vessel  aluminium  silicate,  so- 
dium sulphate,  soda,  sulphur,  and  charcoal  is  used 
exclusively  in  paints.  The  resultant  pigment  con- 
tains SiO2,  A12O3,  Na2O,  SO3,  and  S  with  traces  of 
water,  lime,  iron,  etc.  The  manner  in  which  these 
materials  are  combined  to  produce  the  blue  is  not 
well  understood. 

The  tone  of  the  color  varies  from  greenish  to 
purplish,  the  analysis  seeming  to  show  that  the  per- 
centage of  silicon  increases  and  the  aluminium  de- 
creases from  the  green  to  the  purple. 

Ultramarine  blue  is  not  effected  by  heat  or  dilute 
alkali,  but  is  at  once  destroyed  by  acid  with  the 
evolution  of  H2S.  This  gives  a  ready  method  of 
distinguishing  it  from  cyanogen  blues.  It  usually 
contains  about  42  per  cent  SiO2  and  25  per  cent 
A12O3,  though  both  these  amounts  increase  and  di- 
minish through  narrow  limits  in  different  shades. 
As  one  increases  the  other  diminishes.  Owing  to 
its  peculiar  composition  and  to  the  fact  that  it  con- 
tains soluble  silicates  the  analysis  of  ultramarine 
blue  becomes  complicated. 

METHOD  OF  ANALYSIS. — Weigh  out  2  gms.  sample, 
treat  with  dilute  HC1,  evaporate  to  dryness  and  heat 


RAW  MATERIALS  19 

for  one  hour  at  a  temperature  between  110°  and 
120°  C.  Add  a  small  amount  of  HC1  and  repeat. 
This  renders  all  silicic  acid  formed  insoluble. 
Treat  with  HCl,  boil,  decant  on  filter,  and  repeat. 
Wash  residue  free"  from  acid,  dry,  ignite,  and  weigh 
as  SiO2.  Examine  for  barytes,  china  clay,  etc.,  by 
S.  I.  or  S.  I.  a. 

Make  filtrate  up  to  500  c.c.  Take  250  c.c., 
make  alkaline  with  NH4OH,  boil,  decant  on  filter, 
wash,  dry,  ignite,  and  weigh  precipitate  as  A12O3. 
Any  calcium  may  be  precipitated  from  filtrate  with 
ammonium  oxalate. 

To  the  other  portion  of  250  c.c.,  after  heating, 
add  a  boiling  solution  of  BaCl2  and  determine  sul- 
phates in  the  usual  manner.  Calculate  to  SO3. 

To  determine  S,  oxidize  with  fuming  HNO3, 
in  a  closed  flask.  Add  some  NaCl,  evaporate  to 
dryness,  and  heat  at  110°  to  120°  for  one  hour. 
Treat  with  dilute  HCl,  re-evaporate  and  again 
treat  with  HCl,  filter  out  SiO2,  and  precipitate 
boiling  with  barium  chloride  solution  as  in  the  de- 
termination of  sulphate.  After  subtracting  sul- 
phate existing  as  SO3,  calculate  remainder  to  S. 

Obtain  Na2O  by  difference  after  all  other  materials 
have  been  determined,  or  to  the  filtrate  from  the 
aluminia  add  an  excess  of  H2SO4,  concentrate,  and 
evaporate  to  dryness  in  a  platinum  dish  by  care- 
fully igniting  at  a  low  temperature  just  sufficient 
to  drive  off  the  ammonium  salts  and  excess  of 
Weigh  the  sodium  as 


20          THE  CHEMISTRY  OF  PAINTS 

BLACK  PIGMENTS 

Ivory  and  Bone  Black.  —  These  pigments  are  com- 
binations of  carbon,  hydrocarbons,  water,  and  min- 
eral matter;  their  value  as  pigments  depends  upon 
their  blackness  and  strength.  The  presence  of  oily 
matter  is  detrimental,  as  it  retards  drying  when 
mixed  with  oil.  Test  for  this  by  dissolving  out  with 
ether.  To  make  an  ANALYSIS  of  these  pigments, 
weigh  out  i  gm.  sample  (in  absence  of  carbonate)  in 
a  porcelain  crucible,  then  place  lid  on  so  that  there 
remains  a  very  small  opening,  and  ignite  at  low  heat 
until  no  more  vapor  is  driven  off.  Cool,  weigh,  and 
express  difference  as  water  and  hydrocarbons.  Again 
ignite,  very  strongly  this  time  with  the  lid  removed, 
until  all  the  carbon  is  driven  off.  This  further  loss 
is  expressed  as  carbon  and  the  residue  as  ash. 

These  blacks  are  rightly  used  in  carriage  painting, 
or  where  an  intense  black  is  desired,  and  never  for 
tinting  purposes,  owing  to  their  weak  tinting  power. 

Carbon  Black,  or  Gas  Black.  —  This  pigment  is 
not  so  black  as  the  best  grade  of  ivory  and  bone 
blacks,  but  as  black  as  some  of  the  cheaper  grades. 
It  is  very  bulky,  ij  Ibs.  requiring  about  i  gallon  of 
oil  to  grind  to  a  paste.  It  is  a  combination  of  carbon 
and  hydrocarbons,  and,  like  ivory  and  bone  blacks, 
should  be  as  free  from  oily  matter  as  possible  since 
any  large  amount  of  this  present  not  only  impairs 
the  drying  property  to  a  very  great  extent,  but  might 
make  the  pigment  dangerous  to  store,  owing  to 
the  possibility  of  spontaneous  combustion. 


RAW  MATERIALS  21 

Carbon  black  has  a  very  strong  tinting  power,  but 
gives  a  dirty  brown  tint  when  compared  to  lamp 
black,  and  on  this  account  is  little  used  for  this 
purpose.  It  finds  its  chief  use  in  the  manufacture 
of  black  paints,  where  so  intense  a  black  as  that 
given  by  bone  and  ivory  blacks  is  not  required.  It 
may  be  assayed  in  the  same  manner  as  bone  black, 
and  should  leave  no  ash. 

Lamp  Black.  —  This  pigment  has  a  dark  gray 
shade  in  oil,  and  finds  its  chief  use  in  tinting.  With 
white  lead  and  zinc,  good  grades  of  lamp  black 
give  a  very  clear  bluish  tone,  and  this  should  always 
be  taken  into  consideration  in  comparing  samples. 
Its  shade  in  oil  matters  little,  as,  where  a  black  for 
painting  is  desired,  carbon  or  bone  black  may  be 
used.  In  strength  it  is  inferior  to  carbon  black, 
but  its  superior  tint  more  than  makes  up  for  this 
deficiency.  It  should  always  be  used  where  clear 
tints  are  desired. 

Like  the  other  blacks  it  should  be  quite  free  from 
oily  matter  and  should  always  be  tested  for  this 
impurity.  All  other  things  being  equal,  the  lamp 
black  containing  the  least  amount  of  oily  material 
is  to  be  preferred.  Its  absence,  however,  is  not 
so  important  a  matter  in  the  case  of  lamp  blacks 
as  in  the  other  blacks,  since  this  pigment  is  gener- 
ally used  only  for  tinting  purposes,  and  any  oil  in 
the  small  quantity  of  black  used  as  a  tinter  will 
have  little  effect  on  the  drying  of  the  paint. 


22  THE  CHEMISTRY  OF  PAINTS 

It  may  be  assayed  in  the  same  manner  as  carbon 
black,  and  like  the  latter  should  yield  no  ash. 

BROWN  PIGMENTS 

Umbers.  —  "Raw"  umber  is  a  natural  earthy 
material,  the  shade  of  which  varies  greatly,  owing 
to  the  wide  variation  in  the  proportions  of  MnO2  and 
Fe2O3  which  are  contained  in  it.  After  calcining 
it  assumes  a  darker,  "warmer"  color,  and  is  known 
as  burnt  umber.  Its  value  depends  upon  its  shade, 
strength,  and  fineness. 

METHOD  OF  ANALYSIS.  —  To  determine  the  per- 
centage of  manganese  follow  M.  II.,  using  for  a  com- 
plete analysis  i  gm.  of  the  substance.  In  the  case 
of  burnt  umber  long  continued  boiling  with  HC1 
will  be  necessary  to  effect  solution,  owing  to  the  fact 
that  oxides  of  iron  and  manganese  are  rendered 
difficultly  soluble  by  calcining.  After  digesting  in 
the  acid,  filter,  then  dry,  ignite,  and  weigh  the 
insoluble  residue,  and  finally  separate  it  by  S.  I.  or 
S.  I.  a.  (In  the  analysis  of  all  earthy  pigments 
where  prolonged  digestion  is  necessary  to  effect 
solution,  it  is  best  to  evaporate  to  dryness,  heat  for 
one  hour  at  110°  C.,  and  again  dissolve  in  HC1  in 
order  to  render  insoluble  any  silicic  acid  that  may 
be  formed  by  the  decomposition  of  the  silicates 
present.)  Make  the  filtrate  alkaline  with  NaOH 
then  boil,  wash  thoroughly,  filter,  dry,  ignite  precip- 
itate and  paper  separately,  and  weigh  the  combined 
oxides  of  iron  and  manganese,  and  finally  separate  by 


RAW  MATERIALS  23 

M.  III.,  or  by  other  suitable  methods.  Precipitate 
the  filtrate  with  ammonium  oxalate,  filter,  and  treat 
the  precipitate  of  calcium  oxalate  by  C.  I. 

Manganese  present  as  MnO2  may  be  determined 
by  M.  IV. 

Determine  CO2  by  C.  III.,  using  a  separate  sample 
of  5  gms. 

Dissolve  in  HC1  and  determine  SO3  by  S.  II. 

Usually  all  that  is  necessary  to  know  about  an 
umber  is  the  percentage  of  constituents  not  MnO2 
and  Fe2O3,  so  as  to  be  able  to  make  allowance  for 
them  when  matching  a  sample  of  umber,  or  an 
umber  tinted  color.  In  the  analysis,  therefore,  the 
oxides  of  iron  and  manganese  may  be  discarded 
(or  weighed  together  without  separating)  and  only 
the  other  constituents  determined. 

Vandyke  Brown.  —  This  substance  is  largely  or- 
ganic and  is  found  in  nature.  It  also  is  manufac- 
tured by  calcining  organic  matter  of  plant  origin 
in  a  closed  vessel  and  by  mixing  black  pigments 
with  red  oxides  and  ochres.  It  resembles  the 
blacks  somewhat  in  composition,  but  contains  a 
smaller  percentage  of  carbon  and  a  larger  per- 
centage of  hydrocarbons,  and  these  constituents, 
together  with  the  earthy  materials  present,  give  it 
the  color.  Its  ANALYSIS  is  rather  complicated,  but  fair 
results  may  be  obtained  by  a  combination  of  methods 
applied  to  carbon  black  and  umber.  The  CO2 
present  must  be  obtained  by  C.  III.  on  a  separate 
sample.  If  not  present  the  hydrocarbons  are 


24  THE  CHEMISTRY  OF  PAINTS 

obtained  in  the  same  manner  as  in  blacks.  To  de- 
termine carbon  in  the  presence  of  carbonates,  the 
sample  is  dissolved  in  HC1,  the  insoluble  carbon 
filtered  on  a  Gooch  crucible,  dried,  weighed,  ignited 
until  all  carbon  is  consumed,  again  weighed,  and 
carbon  obtained  by  difference.  The  metals  in 
solution  in  HC1  should  be  determined  as  in  the 
analysis  of  umber.  Alkali  carbonates  will  be 
found  in  some  samples. 

Graphite.  —  This  material  is  found  in  nature 
and  is  an  allotropic  form  of  carbon.  It  is  of  a  brown- 
ish gray  color,  very  greasy  to  the  touch,  and  the 
finer  grades  are  used  in  lead  pencils  and  lubri- 
cants. The  grade  used  in  paints  contains  a  con- 
siderable percentage  of  silica,  with  small  amounts 
of  other  materials.  This  substance  is  unaffected 
by  all  ordinary  acids  and  alkalies,  and  by  the 
weather.  On  this  account  it  is  largely  used  for 
coating  structural  iron  work  and  ship  bottoms,  and 
for  these  and  similar  purposes  it  has  proved  to  be 
superior  to  any  other  material. 

METHOD  OF  ANALYSIS. — To  get  the  percentage  of 
graphite,  boil  with  diluted  HC1,  filter  on  a  platinum 
Gooch,  dry  in  an  oven  to  constant  weight,  ignite  over 
blast  until  the  graphite  is  driven  off,  and  get  graphite 
by  loss.  In  the  absence  of  carbonates  the  graphite 
may  be  estimated  in  the  same  manner  as  carbon  in 
blacks.  A  platinum  instead  of  a  porcelain  crucible 
should  be  used,  however,  and  it  will  be  found  neces- 
sary to  ignite  the  sample  much  longer  and  at  a  higher 


RAW  MATERIALS  25 

temperature  than  in  the  case  of  blacks.  A  sample 
of  from  .25  to  .5  gms.  will  be  found  more  easily 
manipulated  than  i  gm.,  owing  to  the  less  combus- 
tible nature  of  graphite.  The  non-combustible  resi- 
due may  be  analyzed  by  S.  I.  or  S.  I.  a. 

_,_x 

GREEN  PIGMENTS 

Chrome  Green.  —  This  pigment  is  a  mixture  of 
chrome  yellow  and  Chinese  blue,  and  taking  all 
properties  into  consideration  it  is  the  most  satis- 
factory green  made.  The  shade  varies  with  the 
proportions  of  blue  and  yellow  and  with  the  method 
of  making.  Thus,  a  green  made  by  precipitating 
a  yellow  made  from  acetate  of  lead  on  the  blue 
has  a  yellowish  shade  and  bluish  tint,  but  if  nitrate 
of  lead  and  white  lead  are  substituted  for  the  ace- 
tate a  bluish  green  with  a  yellowish  tint  is  obtained. 
The  finest  greens  are  obtained  by  combining  these 
two  methods  and  by  properly  manipulating  the 
materials  used.  The  mere  grinding  together  of 
blue  and  yellow  will  not  produce  shades  which  at 
all  compare  in  brightness  with  those  obtained  by 
precipitating  the  colors  together. 

METHOD  OF  ANALYSIS.  —  The  color  of  chrome 
green  is,  like  that  of  Chinese  and  Prussian  blue,  im- 
mediately destroyed  by  fixed  alkalies  and  heat.  The 
usual  adulterants  are  barytes,  china  clay,  and  very 
rarely  whiting  and  gypsum.  To  estimate  them,  pro- 
ceed as  in  Dry  Colors.  In  case  the  percentages  of 
yellow  and  blue  are  desired,  determine  the  percent- 


26  THE  CHEMISTRY  OF  PAINTS 

age  of  adulterants  as  in  Dry  Colors,  and  the  per- 
centage of  yellow  as  in  Chrome  Yellow,  and  obtain 
the  percentage  of  blue  by  difference. 

RED  PIGMENTS 

Iron  Oxide.  —  This  material  exists  in  nature  as 
hematite  and  limionite  and  is  the  chief  ore  of  iron. 
Many  of  the  oxides  on  the  market  are  obtained 
from  the  natural  source  and  hence  are  found  to 
vary  widely  in  composition,  some  containing  as 
little  as  10  per  cent  ferric  oxide,  whereas  others  are 
practically  pure.  The  shade  will  vary  from  a  dull 
reddish  brown  (due  to  presence  of  MnO2)  to  a 
bright  reddish  color.  Very  bright  oxides  are  pro- 
duced artificially  by  calcining  copperas  and  may  be 
procured  pure. 

The  value  of  this  pigment  depends  upon  its 
shade  in  oil,  percentage  of  oxide  of  iron,  and  its 
freedom  from  grit.  ANALYZE  as  in  umber,  substi- 
tuting NH4OH  in  place  of  NaOH.  The  presence  of 
any  dye  may  be  determined  by  adding  alcohol  to  a 
small  sample  and  observing  whether  or  not  any 
color  is  dissolved.  If  so  the  amount  may  be  cal- 
culated by  difference  after  all  other  constituents 
have  been  determined,  or  in  the  absence  of  com- 
bined water  and  carbonates  by  direct  ignition. 
Alizarine  is  almost  exclusively  used  for  the  produc- 
tion of  Tuscan  and  Indian  Reds.  Zinc  oxide  may 
sometimes  be  found  in  both  of  these  products. 

Natural  oxides  are  likely  to  contain  traces  of 


RAW  MATERIALS  27 

phosphates,  sulphides,  etc.,  and  to  get  an  absolutely 
correct  analysis  should  be  treated  as  in  the  analysis 
of  iron  ores  for  smelting  purposes.  This  involves 
much  work,  however,  and  the  results  are  of  no  value 
to  the  paint  maker. 

VERMILION   PIGMENTS 

English  Vermilion  (HgS).  —  This  pigment  occurs 
in  nature  as  the  mineral  cinnabar,  but  rarely  of 
sufficient  brightness  to  permit  of  its  being  used  as  a 
vermilion.  The  manufactured  article  is  a  very 
bright  vermilion,  but  owing  to  its  cost  has  been 
almost  entirely  displaced  by  the  vermilion  made 
from  orange  mineral.  In  permanency  it  is  declared 
by  some  to  be  the  best  of  the  vermilions,  but  this 
is  open  to  dispute.  It  is  insoluble  in  all  ordinary 
acids  and  alkali,  and  on  burning  leaves  no  ash, 
depositing  metallic  mercury  near  the  top  of  the 
crucible,  if  not  too  hot.  This  gives  a  ready  method 
of  testing  its  purity,  as  any  material  added  as  an 
adulterant  will  be  left  behind  in  the  crucible. 

Red  Lead  and  Orange  Mineral  Vermilion.  — 
This  vermilion,  which  has  practically  displaced 
mercury  vermilion,  is  made  by  precipitating  an 
cosine  or  scarlet  dye  (sometimes  permanent  red) 
on  red  lead  or  orange  mineral.  In  the  case  of 
eosine  it  is  precipitated  with  some  lead  salt,  usually 
lead  nitrate.  The  shade  thus  produced  is  superior 
in  brilliancy  to  English  vermilion,  but  is  not  at  all 
permanent  to  light.  Scarlet  is  precipitated  with 


28  THE  CHEMISTRY  OF  PAINTS 

barium  chloride,  and  while  this  does  not  give  so 
bright  a  vermilion  as  eosine  it  nevertheless  gives  a 
more  permanent  color,  and  is  sometimes  used  for 
dark  shades.  Sulphate  of  barium  must  always  be 
precipitated  with  the  scarlet,  otherwise  an  inferior 
shade  is  produced.  Adulteration  of  these  vermilions 
is  usually  made  with  barytes,  but  where  a  vermilion 
for  dipping  purpose  is  desired,  china  clay  and 
whiting  are  used.  For  ANALYSIS  see  Dry  Colors, 
Chapter  III. 

Permanent  Red,  Para  Red.  —  This  vermilion, 
which  has  recently  been  greatly  in  demand,  is  pro- 
duced by  diazotizing  para  nitranaline  and  combining 
with  beta  naphthol,  usually  on  a  barytes,  whiting,  or 
china  clay  base.  Sometimes  red  lead,  orange  min- 
eral, or  zinc  are  used,  but  not  as  a  usual  thing.  In 
the  case  of  the  pure  color  on  barytes  this  pigment  is 
superior  to  all  other  vermilions  in  permanency,  but 
when  mixed  with  orange  mineral  or  zinc  it  loses  some 
of  this  property.  It  is  unaffected  by  dilute  alkali 
and  by  dilute  HC1  and  H2SO4,  but  is  dissolved  by 
acetic  acid.  Concentrated  HC1  dissolves  it  in  small 
quantities,  while  with  concentrated  H2SO4  it  dis- 
solves to  a  deep  purple,  the  color  returning  on  dilut- 
ing. If  a  small  quantity  of  dry  alkali  is  placed  in  a 
test  tube  with  it,  and  some  alcohol  poured  in,  the 
same  reaction  takes  place.  For  quantitative  ANALY- 
SIS see  Dry  Colors,  Chapter  III. 

In  addition  to  para  nitranaline  other  diazotizable 
bases  are  treated  and  combined  with  beta  naphthol 


RAW  MATERIALS 


29 


in  a  like  manner.  Of  these,  the  ones  generally  used 
are;  alpha  naphtylamine,  which  produces  a  maroon; 
and  ortho  anisidine,  which  produces  a  light  ver- 
milion shade  of  red. 

When  it  is  desired  to  know  what  dye  is  present  in 
a  vermilion  or  red  lake,  it  may  be  determined  by 
the  following  tests:  — 


REAGENT 


SOURCE  OF  COLOR 


ALIZARINE 

EOSINE 

PARA 
NITRANALINE 

ORTHO- 
ANISIDINE 

SCARLET 
(2R) 

H2S04 
Cone. 

HC1 
Cone. 

Dark  brown 
with  reddish 
undertone 
becoming 
light  yellow 
on  diluting. 

Changes  to 
yellow. 
Fluorescent 
solution  with 
excess  of 
NaOH. 

Purple. 
Color  re- 
turning on 
diluting. 

Purple. 
Red  on 
diluting. 

Darkened. 
Lighter  on 
diluting. 

Color 
becomes 
"  Muddy." 

Changes  to 
yellow.  Red- 
dish fluores- 
cent solution 
with  excess 
of  NaOH. 

Color 
slightly 
darkened. 
Lighter  on 
diluting. 

Dark 
purplish  red. 
Lighter  on 
diluting. 

Darkened. 
Lighter  on 
diluting. 

NaOH. 
Cone.  sol. 

Dark  reddish 
brown. 
Little  change 
on  diluting. 

Little  change 
Fluorescent 
solution  on 
diluting. 

Color 
changed  to 
brownish  red 
Light  red  on 
diluting. 

Little 
change. 

Reddish 
solution  on 
diluting. 

Alcohol. 

Insoluble. 

Reddish 

fluorescent 
solution. 

Slight 
yellowish, 
orange 
solution. 

Slight 
reddish 
solution. 

NaOH 
Cone,  and 
Alcohol. 

Purplish, 
dark  brown 
on  diluting. 

Purple. 
Color 
returning  on 
diluting. 

Little 
change. 

Color  darker. 
Reddish 
solution  on 
diluting. 

30          THE  CHEMISTRY  OF  PAINTS 

American    Vermilion,   Basic    Lead    Chromate. — 

This  vermilion  is  manufactured  by  heating  together 
in  water,  white  lead,  sodium,  or  potassium  bi- 
chromate and  soda  ash,  until  the  color  no  longer 
change  on  further  heating,  and  finally  adding  a 
small  amount  of  sulphuric  acid  to  brighten  the  shade. 
It  has  but  little  body  or  brightness,  and  owing  to  its 
peculiar  crystalline  nature  has  a  tendency  to  settle 
rapidly  in  oil.  It  is  very  permanent,  however,  and 
on  this  account  has  been  in  considerable  demand. 
Until  recently  it  has  often  been  used  in  conjunction 
with  eosine  vermilions,  and  when  so  used  the 
resultant  vermilion  becomes  very  difficult  to  analyze, 
owing  to  the  varying  composition  of  both  materials. 
For  approximate  analysis  and  separation  of  such  a 
material  see  Analysis  of  Dry  Colors.  Since  the 
introduction  of  Para  reds,  American  vermilion  has 
fallen  into  disuse. 

WHITE  PIGMENTS  AND  ADULTERANTS 

Barytes  (BaSO4).  —  This  material,  which  is  the 
most  widely  used  of  any  adulterant,  is  found  in 
nature  in  large  quantities  as  natural  sulphate  of 
barium.  It  is  very  heavy  and  on  this  account  is 
much  used  for  adulterating  white  lead.  It  does  not 
grind  well  with  oil,  however,  being  "  short, "  probably 
owing  to  its  crystalline  nature,  and  it  has  a 
tendency  to  settle  into  a  very  hard  mass.  On 
this  account  it  is  not  advisable  to  use  it  in  mixed 
paints. 


RAW  MATERIALS  31 

Barytes  has  very  little  opacity,  having  no  effect  on 
the  shade  in  oil  of  a  strong  color  even  when  added  in 
large  quantities.  It  should  be  very  white  and  without 
grit.  It  is  insoluble  in  all  ordinary  acids  and  alkalies 
and  in  all  concentrated  acids  except  hot  H2SO4,  in 
which  it  dissolves  again  separating  on  diluting. 
For  ANALYSIS  boil  one  gram  (i  gm.)  in  dilute  HC1, 
filter,  wash  thoroughly,  dry,  ignite  in  porcelain 
crucible,  and  weigh  the  insoluble  material,  which 
will  be  BaSO4,  and  any  silica  or  silicates  which  may 
be  present.  The  latter  will  rarely  or  never  be 
present,  but  the  insoluble  residue  may  be  tested 
by  S.  I.  If  any  silica  or  silicates  are  present, 
even  in  small  quantities,  an  effervescence  will  be 
noticed  on  the  addition  of  HF  and  the  bottom  of 
the  platinum  crucible  will  become  warm. 

The  filtrate  may  be  tested  by  making  alkaline 
with  ammonia  and  boiling.  A  precipitate  will  be 
hydrates  of  iron  and  aluminium.  Filter,  dry, 
ignite,  and  weigh  as  Fe2O3  and  A12O3.  It  will 
not  be  necessary  to  separate  or  to  make  certain 
whether  both  are  present.  Test  filtrate  for  cal- 
cium by  precipitating  hot  with1  ammonium  oxa- 
late.  Determine  soluble  sulphate  by  dissolving 
i  gm.  in  HC1,  filtering,  and  precipitating  with  BaCl2, 
calculating  the  BaSO4  thus  produced  to  CaSO4  by 
the  proper  factor.  Any  calcium  not  satisfied  by 
the  sulphate  is,  in  the  presence  of  carbonates,  cal- 
culated to  whiting  (CaCO3),  or  if  no  carbonates  are 
present,  to  lime  (CaO).  Water  and  moisture  are 


32  THE  CHEMISTRY  OF  PAINTS 

determined  by  heating  the  original  sample  if  car- 
bonates are  not  present. 

China  Clay  (2SiO2Al2O3+2H2O).  —  This  is  a 
light,  bulky  clay  with  but  little  opacity,  being  essen- 
tially a  hydrated  silicate  of  aluminium.  It  may  be 
ANALYZED  by  S.  I.  or  S.  I.  a,  the  percentage  of  free 
H2O  obtained  by  drying  the  sample  at  100°  and 
that  combined  by  ignition  of  i  gm.  in  a  porcelain 
crucible,  subtracting  the  amount  found  free. 

When  china  clay  is  encountered  in  an  analysis 
of  a  paint  or  dry  color,  this  combined  water  must 
be  taken  into  consideration  and  calculated  from  the 
per  cent  A12O3  present,  with  which  it  seems  to  vary 
in  a  fairly  constant  ratio  of  about  1:3.  Take  a 
paste,  for  instance,  in  which  75  per  cent  of  insoluble 
material  has  been  found.  After  separating  by  S.  I., 
50  per  cent  BaSO4  is  found  and  10  per  cent  A12O3. 
This  by  difference  gives  us  15  per  cent  SiO2.  But 
in  the  added  China  clay  there  was  an  amount  of 
water  averaging  J  of  the  A12O3  present,  which  was 
lost  on  igniting  the  insoluble  residue.  So  J  of  10 
=  3^,  and  our  result  of  analysis  of  the  insoluble 
material  becomes 

50%  Barytes 
28J%  China  clay 


Total       78^% 

China  Clay  is  insoluble  in  ordinary  alkalies  and 
acids,   but   gradually   decomposes  into  aluminium 


RAW  MATERIALS  33 

sulphate  and  silicic  acid  with  hot  concentrated 
H2SO4. 

Gypsum,  Natural  Sulphate  of  Calcium  (CaSO4 
+  2H2O).  —  A  white  mineral  with  trifling  opacity, 
formerly  used  widely  as  an  adulterant  but  at  the 
present  time  very  seldom  encountered.  Its  ANALYSIS 
consists  in  determining  the  materials  insoluble  in 
acid,Fe203,  A12O3,  CaO,  SO3,  CO2,  and  H2O.  When 
dehydrated  it  is  widely  used  under  the  name  of 
Plaster  of  Paris. 

Carbonate  of  Magnesium  (MgCO3).  —  This  is  the 
lightest,  most  bulky  white  used.  It  is  never  en- 
countered in  mixed  paints  or  pastes,  and  its  use 
in  all  paint  products  is  limited,  but  it  is  sometimes 
used  in  wood  filters.  Its  ANALYSIS  would  consist 
in  determining  the  CO2  present  by  C.  III.,  dissolving 
i  gm.  in  HC1,  and  determining  the  insoluble  material, 
Fe2O3,  A12O3,  and  calcium  in  the  solution,  and  after 
these  materials  are  precipitated  treating  the  filtrate 
as  in  M.  I.  for  magnesium. 

Silicate  of  Magnesium.  —  A  light,  bulky  silicate 
of  no  opacity,  but  used  to  a  considerable  extent  to 
adulterate  mixed  paints.  It  is  a  chemical  com- 
bination of  MgO  and  SiO2,  usually  in  the  propor- 
tion of  35  per  cent  MgO  and  60  per  cent  SiO2,  with 
small  quantities  of  A12O3,  Fe2O3,  MgO,  CaO,  H2O, 
etc.  It  does  not  grind  readily  with  oil,  unless  a  large 
proportion  of  the  latter  is  present,  and  hence  re- 
sembles barytes  in  this  respect.  It  is  insoluble  in 


34          THE  CHEMISTRY  OF  PAINTS 

ordinary  dilute  acids  and  alkalies.     For  ANALYSIS 
proceed  as  in  S.  I. 

Silica  (SiO2).  —  A  pigment  without  opacity,  not 
much  used  in  pastes  or  mixed  paints,  but  forming 
a  main  constituent  of  iron  and  wood  filters.  Its 
value  depends  upon  its  whiteness  and  fineness. 
Silica  containing  much  grit  has  a  very  bad  effect 
upon  the  mills.  Its  purity  may  be  readily  obtained 
by  S.  I. 

SUBLIMED  LEADS  AND  ZINC 

Sublimed  Lead.  —  This  material,  which  is  found 
on  the  market  as  a  substitute  for  white  lead,  is 
different  from  that  material  in  a  great  many  of  its 
properties.  It  is  less  poisonous  and  less  susceptible 
to  the  action  of  gases  and  impure  atmosphere. 
The  commercial  article  is  made  by  volatilizing 
galena  (PbS)  and  converting  it  by  oxidation  into 
PbSO4.  As  it  is  nearly  impossible  to  obtain  galena 
free  from  sphalerite  (ZnS),  zinc  oxide  will  always 
be  found  admixed  with  it.  Oxides  of  lead  also 
occur  in  this  pigment  in  some  peculiar  form  of  PbO. 

A  sample  analyzed  by  the  author  was  shown  to 
have  the  following  composition: 

PbSO4  =  78.60% 

PbO  =  13.80% 

ZnO=  5.50% 
ZnS04=  1.63% 

H20=  .13% 
Total  99-66% 


RAW  MATERIALS  35 

The  above  analysis  was  made  several  years  ago 
and  the  pigment  as  now  produced  shows  zinc  &1- 
phate  only  in  traces.  The  pigment  necessarily 
varies  somewhat  from  time  to  time  in  percentage 
of  constituents.  The  manufacturers  give  the  fol- 
lowing as  an  approximate  analysis: 

PbSO4=75%  )Lead  oxy-sulphate,  or 
PbO  =  20%  )  Basic  lead  sulphate 
ZnO=  5% 

It  will  be  noted  that  the  manufacturers  claim 
that  the  lead  oxide  present  is  chemically  combined 
with  the  lead  sulphate  in  the  form  of  basic  lead 
sulphate.  While  there  is  some  basis  for  such  a 
claim  the  evidence  is  not  at  all  conclusive. 

Many  obstacles  have  been  encountered  by  the 
manufacturers  in  making  this  product  satisfactory. 
They  claim  to  have  overcome  them  and  the  more 
extensive  use  of  this  pigment  would  seem  to  confirm 
their  assertions. 

Zinc  Lead.  —  This  is  made  from  a  combination 
of  zinc  and  lead  ores.     Samples  analyzed  by  the 
author  had  the  following  composition: 
PbS04  =  54-48%—  51.52% 
ZnO  =  41.44%  — 47-12% 
ZnSO4=   2.16%  —    0.85% 
H20=     .52%-      .18% 
Total         98.60%  — 99.67% 
The  second  analysis  is  the  more  recent.     The 
present  standard  requires  zinc  sulphate  to  be  present 
in  quantities  less  than  i  %. 


36          THE  CHEMISTRY  OF  PAINTS 

This  pigment  falls  about  midway  between  sub- 
limed lead  and  American  zinc  in  its  chemical 
composition,  excepting  that  it  is  free  from  lead 
oxide.  Although  its  use  by  many  manufacturers 
is  general,  it  probably  finds  its  widest  use  in  the 
manufacture  of  paste  primers. 

American  Zinc.  —  This  is  made  by  roasting 
sphalerite  (ZnS)  and  converting  it  into  ZnO.  It 
always  contains  small  quantities  of  lead  which 
occur  with  it  in  the  ore.  The  following  is  the 
composition  of  two  different  grades  as  determined 
by  the  author,  No.  I.  being  the  better  and  No.  II.  the 
inferior  grade. 

I.  II. 

Insol.  matter  =  0.50%  Insol.  matter  =  0.10% 

PbS04=  4-96%  PbS04=  13.16% 

ZnO  =91.53%  ZnO  =  82.00% 

PbO  =   1.67%  PbO=   i. 06% 

ZnS04=   1.42%  ZnS04=  3.73% 

Total       100.08%  Total         100.05% 

The  best  grades  of  sublimed  zincs  are  practically 
free  from  oxides  of  lead  and  are  widely  used  for 
mixed  paints.  Pound  for  pound  they  have  better 
body  than  white  lead,  but  bulk  for  bulk  their  body 
is  inferior.  They  are,  on  the  whole,  quite  satis- 
factory pigments  to  use. 

It  is  quite  certain  that  the  composition  of  all  these 
sublimed  products  is  more  complex  than  is  ex- 


RAW  MATERIALS  37 

pressed  by  these  analyses,  traces  of  sulphides,  sul- 
phites etc.,  being  present.  Arsenic  will  generally 
be  found,  especially  in  zinc,  but  in  too  small 
quantities  to  admit  of  determination.  The  fol- 
lowing method  will  fulfil  all  demands  for  their 
analysis: — 

METHOD  OF  ANALYSIS.  —  Dissolve  i  gm.  in  boil- 
ing dilute  HC1  (see  analysis  of  paste  and  tinted 
paints,  Chapter  III,  for  the  proper  mode  of  solu- 
tion), filter,  washing  with  boiling  water  until  all 
lead  chloride  on  filter  is  dissolved.  There  should 
be  little  or  no  insoluble  material,  but  in  case  there 
is,  dry,  ignite,  and  weigh.  If  a  globule  of  lead  is 
found  in  the  crucible,  this  shows  that  the  sample 
has  not  been  properly  treated,  and  another  sample 
must  be  taken.  Heat  filtrate  until  all  the  lead 
chloride  is  dissolved,  make  alkaline  with  ammonia, 
saturate  with  H2S,  and  filter.  The  filtrate  may  be 
discarded,  as  calcium  will  never  be  found  in  these 
materials  when  dry.  Dissolve  the  well  washed  pre- 
cipitate of  PbS  and  ZnS  with  concentrated  HNO3, 
using  as  little  as  possible,  then  wash  thoroughly  with 
hot  water,  let  cool,  add  carefully  5  c.c.  concen- 
trated H2SO4,  treat  as  in  L.  I.  After  filtering  out 
PbSO4,  determine  zinc  in  the  filtrate  by  Z.  I.  De- 
termine sulphates  on  a  separate  sample  by  S.  II., 
deduct  amount  due  to  zinc  sulphate  present,  cal- 
culate the  remainder  to  sulphate  of  lead  by  proper 
factor,  and  calculate  remaining  lead  sulphate  to 
PbO  by  proper  factor.  Express  zinc  found  as 


38          THE  CHEMISTRY  OF  PAINTS 

ZnO  after  deducting  zinc  sulphate  found  by  dis- 
solving separate  sample  in  a  mixture  of  water  and 
alcohol,  filtering,  and  precipitating  with  BaCl2.  It  is 
also  well  to  test  the  merits  of  different  grades  of 
sublimed  products  by  their  action  with  gloss  oil. 

RAPID  METHOD  FOR  ANALYSIS  OF  SUBLIMED 
PRODUCTS.  —  Determine  H2O  on  a  separate  sample 
of  i  gm. 

Boil  i  gm.  with  water  to  which  a  small  amount 
of  alcohol  has  been  added.  Determine  sulphate  in 
solution  and  calculate  as  ZnSO4. 

Determine  total  sulphate  on  a  separate  sample, 
obtaining  insoluble  impurities  at  the  same  time. 
Deduct  amount  sulphate  previously  found  as  ZnSO4 
and  calculate  remainder  as  PbSO4. 

Treat  a  separate  sample  of  i  gm.  with  a  mixture 
of  water,  alcohol,  acetic  and  sulphuric  acid  until  all 
zinc  is  dissolved.  Filter  on  Gooch  crucible,  dry, 
ignite,  and  weigh.  Deduct  amount  of  insoluble 
impurities  previously  obtained,  the  remainder  being 
PbSO4.  Deduct  PbSO4  found  as  calculated  from 
sulphate  present,  and  calculate  remainder  to  PbO. 
Obtain  ZnO  by  difference,  or  precipitate  with 
Na2CO3.  Wash  free  from  sodium  salts,  filter,  dry, 
ignite,  and  weigh  as  ZnO. 

All  of  the  above  determinations  being  made  on 
separate  samples,  they  can  be  carried  on  at  the 
same  time  and  results  obtained  quickly. 

Whiting.  —  This  material,  which  is  the  natural 
carbonate  of  calcium  (CaCO3),  contains  small 


RAW  MATERIALS  39 

amounts  of  CaO,  Fe2O3,  A12O3,  CaSO4,  etc.,  and 
is  as  widely  used  as  an  adulterant  as  barytes,  but 
as  a  usual  thing  only  in  paste  and  mixed  paints,  and 
very  seldom  in  dry  colors,  excepting  permanent 
reds.  With  pure  linseed  oil  it  is  widely  used  in  the 
manufacture  of  putty. 

Whiting  should  always  be  carefully  examined  for 
lime.  This,  if  present  in  any  appreciable  quanti- 
ties, will  be  detrimental.  To  test  for  this,  boil  a 
sample  with  water,  and  add  phenol  phthalein  in- 
dicator. If  a  red  color  is  produced,  the  presence 
of  lime  is  shown.  This  will  often  be  found  to  be 
the  cause  of  a  light  green  or  blue  tint  losing  its 
shade  in  the  can.  The  shade  will  generally  regain 
its  original  color  on  drying  after  being  painted  out. 

An  ANALYSIS  of  whiting  should  be  made  in  the 
same  manner  as  gypsum. 

White  Lead.  —  This  pigment  is  the  most  im- 
portant and  widely  used  white  pigment  with  which 
the  chemist  and  paint  maker  comes  in  contact.  It 
is  properly  made  by  the  old  Dutch  process  of  corrod- 
ing the  metallic  lead  with  weak  acetic  acid  and 
tannin  bark,  or  some  similar  substance.  It  is  used 
as  the  basis  of  all  high-grade  prepared  paints,  fre- 
quently in  conjunction  with  zinc  oxide. 

It  never  will  be  found  adulterated  in  the  dry 
state.  Its  purity,  however,  may  be  tested  by  adding 
dilute  acetic  acid  which  should  dissolve  it  and  leave 
no  residue.  This  acid  also  will  dissolve  any  whit- 
ing or  zinc  present,  and  these  constituents  may  be 


40  THE  CHEMISTRY  OF  PAINTS 

tested  for  in  the  filtrate  by  first  precipitating  the 
lead  with  H2S  in  dilute  acid  solution,  then  testing 
the  filtrate  after  making  alkaline  with  NH4OH, 
for  zinc  with  yellow  ammonia  sulphide  in  excess. 
If  found,  filter  and  test  for  calcium  in  filtrate  with 
ammonia  oxalate.  Barytes  and  sulphate  of  lead 
are  the  materials  chiefly  used  to  adulterate  white 
lead  in  paste  form  and  may  be  readily  determined. 
Pure  white  lead  has  the  following  composition: — 

2PbC03,  Pb(OH)2. 

It  is  a  basic  carbonate  of  lead,  and  not  lead  car- 
bonate as  it  is  usually  called. 

METHOD  OF  ANALYSIS.  —  To  analyze  a  sample  of 
pure  white  lead  for  its  constituent  parts,  dissolve  in 
acetic  acid,  precipitate  with  H2SO4,  dilute  highly, 
add  an  equal  volume  of  alcohol,  filter  on  a  Gooch 
crucible,  dry,  ignite,  and  weigh  as  PbSO4.  Now 
determine  CO2  on  separate  sample  of  5  gms.,  cal- 
culate from  this  the  percentage  of  PbCO3  present, 
and  calculate  remaining  lead  to  Pb(OH)2. 

Analyze  the  adulterated  samples  of  white  lead 
as  in  tinted  pastes  and  paints,  Chapter  III. 

French  Zinc,  Pure  ZnO.  —  This  material  is  made 
from  metallic  zinc  by  heating  in  retorts  until  the 
zinc  is  volatilized,  then  bringing  the  fumes  in  con- 
tact with  air  and  collecting  the  oxide  of  zinc  thus 
formed  in  bags  or  chambers. 

The  material  thus  produced  is  put  upon  the  mar- 
ket in  two  grades,  green  and  red  seal.  The  green 


RAW  MATERIALS  41 

seal  is  the  finer  quality,  being  the  whitest  of  pig- 
ments, and  is  much  used  in  white  enamels  and 
interior  finishes. 

French  zinc  should  contain  no  lead  or  other 
impurities  except  in  traces,  thus  being  as  nearly 
pure  as  it  is  possible  to  obtain  a  commercial  article. 
It  should  dissolve  completely  in  dilute  acetic  acid, 
and  yield  no  precipitate  on  the  addition  of  sul- 
phuric acid  and  alcohol.  When  the  solution  is 
made  alkaline  with  ammonia  and  yellow  ammonia 
sulphide  added,  the  resultant  precipitate  should  be 
pure  white.  The  percentage  ZnO  may  be  deter- 
mined by  Z.  I. 

YELLOW  AND   ORANGE   PIGMENTS 

Chrome  Yellow  (PbCrO4).  —  This  pigment,  which 
is  made  by  precipitating  a  solution  of  some  lead  salt 
(usually  lead  nitrate,  acetate  or  basic  acetate)  with 
sodium  bichromate,  is  the  most  important  yellow 
pigment  in  use.  It  adapts  itself  to  a  wide  variation 
in  shade,  from  the  light  lemon-yellow  made  by  pre- 
cipitating PbSO4  in  conjunction  with  the  PbCrO4 
to  the  very  deep  orange  produced  by  heat  and  the 
addition  of  alkali,  which  forms  more  or  less  basic 
chromate  of  lead.  The  tone  also  is  widely  varied 
in  all  the  shades,  the  addition  of  nitric  acid  giving 
the  yellow  a  much  brighter  cast,  and  when  added 
in  considerable  quantities  producing  a  very  greenish 
tint  in  the  light  shades. 


42  THE  CHEMISTRY  OF  PAINTS 

Pure  chrome  yellow  should  contain  no  foreign 
material  excepting  PbSO4,  which,  however,  cannot 
be  considered  an  impurity,  owing  to  the  fact  that 
it  is  a  necessary  adjunct  in  producing  the  light 
shades.  It  is  soluble  in  HC1  and  HNO3,  producing 
an  intensely  green  solution  caused  by  the  chromic 
salts,  and  this  may,  in  the  analysis  of  paints  and 
dry  colors,  always  be  taken  as  indicative  of  the 
presence  of  chromate  of  lead,  its  presence  in  the 
case  of  vermilions  being  due  to  the  presence  of 
American  vermilion. 

METHOD  OF  ANALYSIS. — If  a  sample  is  adulter- 
ated the  percentage  of  adulteration  may  be  deter- 
mined as  in  dry  colors.  For  analysis  of  a  pure  sample 
boil  with  dilute  HNO3  and  alcohol  until  the  lead 
chromate  is  dissolved.  Let  cool,  add  5  c.c.  H2SO4, 
and  evaporate  to  sulphuric  acid  fumes,  then 
dilute  with  water  and  determine  the  lead  by  L.  I. 
Determine  the  chromium  in  the  filtrate  by  precip- 
itating with  ammonia  and  treating  as  in  C.  IV.  Dis- 
solve in  HC1  and  determine  SO3  by  S.  II. 

Red  Lead  and  Orange  Mineral  (Pb3O4).  —  These 
materials  are  made  by  submitting  lead  or  lead  com- 
pounds to  the  action  of  heat  and  air;  the  former  by 
oxidation  of  metallic  lead,  the  latter  by  oxidation 
of  white  lead. 

They  will  be  found  to  vary  in  shade  from  the  dull 
brownish  yellow  red  lead  of  domestic  manufacture 
to  the  bright  bluish  orange  of  the  imported  material. 
Their  value  depends  upon  their  color  and  body  and 


RAW  MATERIALS  43 

they  should  always  be  tested  for  these  properties. 
The  body  varies  greatly  and  on  this  account  the 
mere  determination  of  the  amount  of  Pb3O4  in  a 
sample  of  vermilion  made  from  them  is  not  suffi- 
cient to  properly  match  it.  A  special  article  on  the 
matching  of  vermilions  containing  orange  mineral 
will  be  found  in  Chapter  IV. 

The  exact  composition  of  red  lead  is  a  matter 
of  much  dispute.  As  a  matter  of  fact  the  com- 
position varies  considerably,  but  it  seems  probable 
that  Pb3O4  expresses  the  correct  composition  and 
that  the  variation  observed  is  due  to  uncombined 
oxides  of  lead  existing  as  an  unavoidable  impurity 
in  the  material. 

The  peculiar  action  of  these  compounds  with 
rosin  varnish  and  the  prevention  of  it  has  troubled 
the  paint  and  varnish  trade  for  many  years.  The 
author  obtained  some  results  which  may  be  found 
of  interest  from  the  paint  standpoint,  and  the  reader 
is  referred  to  his  article  in  the  issue  of  The  Paint, 
Oil  and  Drug  Reporter,  for  Sept.  29,  1902. 

Yellow  Ochre.  —  Yellow  ochre  is  an  earthy  pig- 
ment of  very  dull  shade  in  comparison  to  chrome 
yellow.  It  is  composed  of  a  hydrated  silicate  of 
aluminium  colored  with  iron,  probably  in  the  form 
of  hydrated  ferric  silicate.  Its  value  depends  upon 
its  strength  and  shade.  It  has  fair  body,  and  is 
much  prized  for  primers,  owing  to  its  tendency 
to  penetrate  the  wood,  filling  the  pores.  Its  com- 
position makes  it  permanent  to  all  conditions  of 


44          THE  CHEMISTRY  OF  PAINTS 

the  weather,  and  on  the  whole  it  is  a  very  satis- 
factory pigment. 

Dilute  HNO3  and  HC1  have  little  effect  upon 
yellow  ochres,  except  to  dissolve  very  small  amounts 
of  iron.  Concentrated  HC1  dissolves  all  iron  com- 
pletely on  long  digestion,  leaving  the  white  clay 
behind  insoluble.  Some  aluminium  may  also  be 
dissolved,  and  some  silicic  acid  formed.  It  usually 
will  be  found  to  contain  about  10  per  cent  com- 
bined water.  Standard  French  washed  ochre  is  gen- 
erally considered  as  containing  20  per  cent  iron  oxide 
calculated  as  Fe2O3.  Its  ANALYSIS  may  be  made  by 
S.  I.  or  S.  I.  a.,  separating  iron  and  aluminium  by 
an  appropriate  method. 

Raw  Sienna.  —  Raw  sienna,  like  ochre,  is  an 
earthy  pigment,  being  much  deeper  in  color  and 
varying  considerably  from  the  latter  in  composi- 
tion. Like  ochre,  it  owes  its  color  to  hydrated 
ferric  oxide  (with  small  amounts  of  manganese), 
but  this  is  present  in  much  larger  quantities  than 
in  ochre.  The  American  siennas  usually  contain 
dehydrated  ferric  oxide  in  combination  with  the 
hydrated  oxide,  and  this  gives  them  a  much  redder 
tone  than  the  Italian  siennas  and  at  the  same  time 
increases  their  opacity. 

Burnt  Sienna.  —  This  is  prepared  by  calcining  the 
raw  sienna  at  moderate  heat  until  it  has  acquired 
the  desired  shade.  The  sienna  then  assumes  a 
reddish  yellow  shade  which  is  very  transparent. 
The  change  in  shade  caused  by  calcining  all  earthy 


RAW  MATERIALS  45 

materials  is  due  to  the  driving  off  of  the  combined 
water,  thereby  changing  the  hydrated  ferric  oxide 
to  ferric  oxide. 

Siennas  are  ANALYZED  in  the  same  manner  as 
umbers  and  oxides,  or  may  be  treated  by  S.  I.  or 
S.  I.  a. 


CHAPTER  III 

THE  ANALYSIS  OF  DRY  COLORS,  PASTES,  AND 
LIQUID  PAINTS 

Treatment  of  Sample.  —  In  case  of  pastes  and 
liquid  paints  take  enough  of  the  sample  to  permit 
of  all  necessary  future  tests  and  for  analysis,  put 
it  in  a  suitable  glass  and  add  benzine.  In  the  case 
of  colors  in  japan  and  varnish,  first  wash  thoroughly 
with  turpentine  before  adding  benzine,  as  the  latter 
is  liable  to  precipitate  any  gums  present  on  the 
pigment,  in  which  case  they  will  not  redissolve.  (The 
turpentine  should  be  added  slowly  with  constant 
stirring.)  Set  the  sample  aside  and  let  settle  until 
the  benzine  is  clear,  then  decant,  adding  fresh  ben- 
zine and  repeating  until  the  color  is  free  from  oil. 
The  color  should  be  allowed  to  settle  completely 
before  the  benzine  is  decanted,  otherwise  some  of 
the  lighter  materials  which  do  not  settle  readily 
may  be  lost,  and  thus  the  sample  finally  obtained 
will  not  represent  the  true  proportions  of  constitu- 
ents. 

Dry  the  sample  in  an  air  oven,  grind  with  a 
spatula  on  a  rough  filter  paper  until  it  is  thoroughly 
homogenous  and  pulverized.  If  it  is  properly 
washed  and  not  dried  too  long  it  readily  forms  a 

46 


ANALYSIS  OF  PAINTS  47 

fine  powder.  If  any  particles  of  dried  oil  or  skin 
are  observed,  pass  the  sample  through  an  8o-mesh 
sieve.  This,  however,  should  be  avoided  as  much 
as  possible  by  taking  the  sample  of  paste  from  be- 
low the  surface,  if  the  surface  is  at  all  dried. 

Some  chemists  make  a  practice  of  using  a  cen- 
trifugal machine  in  separating  the  color  from  the 
naphtha,  but  this  will  not  be  found  so  convenient 
as  the  above  method.  Where  great  haste  is  de- 
sired this  plan  has  its  advantages,  but  the  author 
finds  that  by  using  a  vessel  for  washing  of  sufficient 
size,  only  two  washings  are  necessary  to  free  the 
pigment  from  oil,  and  ordinarily  this  may  be  accom- 
plished in  the  course  of  an  hour.  With  very  light 
pigments,  however,  which  stubbornly  stay  in  sus- 
pension, the  centrifugal  machine  is  necessary  to 
make  haste. 

Qualitative  Tests.  —  Test  for  barium  and  calcium 
by  means  of  the  flame  test.  To  do  so,  clean  a  plat- 
inum wire  thoroughly  by  repeatedly  heating  and 
moistening  with  HC1,  then  moisten  with  HC1,  touch- 
ing it  to  the  sample  so  as  to  collect  a  small  amount 
on  the  wire,  and  place  in  the  flame.  A  yellowish 
red  flame,  which  quickly  disappears,  shows  calcium. 
If  barytes  is  present  a  greenish  flame  will  appear. 
Again  moisten  with  HC1,  burn,  and  the  flames  will 
appear  again,  the  green  of  the  barytes  showing 
much  clearer  this  time.  If  this  is  repeated  several 
times  the  calcium  flame  will  be  found  to  disappear 
entirely,  but  the  wire  must  be  moistened  and  burned 


48  THE  CHEMISTRY  OF  PAINTS 

several  times  before  the  barytes  flame  finally  fails 
to  appear.  With  this  test  barytes  can  be  detected 
in  very  small  quantities.  In  the  case  of  calcium, 
however,  especially  if  very  little  is  present  (under 
5  per  cent),  its  presence  might  occasionally  be 
overlooked  and  hence  is  best  checked  by  the  usual 
qualitative  method. 

The  presence  of  gypsum  which,  however,  is  at 
present  very  seldom  encountered  in  samples, 
complicates  the  analysis  somewhat,  and  where  it 
is  suspected  (only  where  sulphates  are  encountered 
in  considerable  quantities)  it  should  be  tested  for 
by  Thompson's  method  as  follows:  Treat  about 
i  gm.  of  the  sample  with  20  c.c.  of  a  mixture  of  i  part 
HNO3  (sp.  gr.  1.2)  and  9  parts  alcohol,  and  let  stand 
for  twenty  minutes.  Decant,  and  repeat  washings 
three  or  four  times  with  the  same  mixture.  Any 
calcium  carbonate  together  with  white  lead  and 
zinc  will  be  dissolved,  while  the  gypsum  will  re- 
main behind  with  the  insoluble  material  which 
may  be  examined  for  calcium.  In  the  absence  of 
CaSO4  all  calcium  may  be  considered  present  as 
CaC03. 

Sulphates  are  tested  for  qualitatively  by  dissol- 
ving in  HC1,  filtering  and  testing  the  filtrate  with 
BaQ2  as  in  the  determination  of  sulphuric  acid. 
(See  S.  II.)  As  sulphates  will  almost  always  be 
found  in  paste  and  liquid  paints  in  varying  quanti- 
ties, it  will  generally  be  found  more  convenient  to 
make  this  test  a  quantitative  one,  and  thus  two 


ANALYSIS  OF  PAINTS  49 

samples  of  the  insoluble  residue  will  be  obtained, 
one  of  which  can  be  tested  for  the  presence  of 
silicates  by  adding  HF  to  it  in  a  platinum  dish, 
evaporating  and  noting  whether  there  has  been  a 
loss  in  weight.  If  not,  the  insoluble  material  is 
pure  barytes;  if  there  has  been  a  loss  it  will  indicate 
silica  or  silicates  (generally  the  latter)  and  the  in- 
soluble residue  from  the  other  weighing  may  be 
treated  by  S.  I. 

Carbonates  will  be  shown  by  effervescence  on 
the  addition  of  acid.  Lead  and  zinc  need  not  be 
tested  for  qualitatively  as  their  presence  will  be 
determined  during  the  quantitative  analysis.  When 
H2S  is  added  to  the  alkaline  solution  the  presence 
of  lead  will  be  indicated  by  the  black  precipitate 
(also  caused  by  iron  whose  presence  will  be  known 
by  a  reddish  precipitate  of  hydrate  when  the  solu- 
tion is  made  alkaline).  If  zinc  also  is  present  the 
precipitate  will  be  grayish  and  the  zinc  sulphide 
will  have  a  tendency  to  remain  in  suspension.  If 
it  is  absent  the  black  precipitate  settles  very  quickly, 
leaving  a  clear  solution.  The  author  only  makes  it 
a  practice  to  make  the  flame  test  for  barytes  and 
calcium,  the  carbonate  test  (may  be  observed  on 
adding  acid  to  weighed  sample  for  quantitative 
analysis)  the  test  for  gypsum  when  calcium  is 
present  and  sulphates  are  found  in  any  quantities, 
and  tests  to  determine  the  character  of  the  color 
when  it  may  be  due  to  different  materials  as  in 
blue  tints  and  vermilions.  For  qualitative  tests  for 


50  THE  CHEMISTRY  OF  PAINTS 

these  materials  see  Ultramarine  and  Permanent 
Vermilion,  Chapter  II. 

Quantitative  Analysis.  —  In  taking  a  sample  for 
analysis  it  is  best  to  weigh  out  exactly  one  or  two 
gms.,  avoiding  fractional  weights.  With  a  little 
practice  this  becomes  easy  and  it  facilitates  the 
work  later  on,  since  it  does  away  with  the  necessity 
of  keeping  a  record  of  the  weight  taken  and  of 
many  subsequent  calculations. 

As  a  solvent  dilute  HC1,  or  in  the  absence  of  lead 
sulphate,  dilute  HNO3  with  a  small  amount  of  alcohol 
added,  may  be  used.  (The  mixing  of  alcohol  with 
HNO3  should  be  accompanied  with  great  caution.) 
In  case  dilute  HC1  is  used  care  must  be  taken  not  to 
mistake  the  lead  chloride  which  is  likely  to  form  in 
the  bottom  of  the  beaker  when  the  solution  is  not 
dilute  enough  or  becomes  cold  with  any  insoluble 
material  present.  It  should  always  be  made  a  point 
to  burn  the  filter  paper  with  the  insoluble  resi- 
due, and  in  case  any  lead  has  been  left  undissolved  it 
will  appear  as  a  metallic  globule  in  the  bottom  of  the 
crucible  surrounded  by  yellow  oxide.  The  author 
uses  HC1  almost  entirely  in  dissolving  paints  and  dry 
colors,  and  has  always  found  it  very  satisfactory 
when  properly  manipulated. 

i.  Analysis  of  Dry  and  Untinted  Paste  Colors 
including  chrome  yellow,  chrome  green,  cyanogen 
blue,  and  vermilions.  Other  colors  should  be  treated 
according  to  methods  given  in  Chapter  II. 

Greens  and   cyanogen   blues  must   be  weighed 


ANALYSIS  OF  PAINTS  51 

in  a  porcelain  crucible  and  ignited  gently  to  break 
up  the  insoluble  blue  (ignition  must  be  at  a  low 
temperature,  otherwise  it  will  be  found  almost 
impossible  to  dissolve  the  Fe2O3  thus  formed). 
For  permanent  reds,  see  i.a.  All  that  is  required 
here  is  to  obtain  the  percentage  of  adulteration, 
the  color  being  calculated  by  difference. 

METHOD. — To  i  gm.  of  the  sample  add  concen- 
trated HC1,  then  about  five  times  as  much  H2O.  Boil 
until  the  color  is  dissolved  and  all  the  lead  con- 
verted into  lead  chloride,  which  can  easily  be  dis- 
tinguished from  any  insoluble  barytes,  china  clay, 
or  silicate  of  magnesium  by  its  crystalline  character. 
If  enough  water  is  present  it  will  all  dissolve  on 
boiling.  Filter,  and  wash  with  boiling  water  until 
certain  that  all  chloride  of  lead  is  washed  out. 
The  residue  may  be  barytes,  china  clay,  or  silicate 
of  magnesium.  Test  and  separate  by  S.  I.  or  S.  I.  a. 
(See  also  Qualitative  Tests.)  Heat  the  filtrate  until 
any  lead  chloride  which  may  have  separated  on 
cooling  has  dissolved,  then  add  NH4OH  until 
alkaline,  and  saturate  with  H2S.  Heat  on  a  hot 
plate,  let  settle,  filter,  wash  thoroughly,  and  deter- 
mine any  calcium  in  the  filtrate  by  C.  I.  This  is 
rarely  found  in  the  above  dry  colors  unless  present 
as  an  impurity  in  the  other  adulterating  materials, 
but  is  generally  found  in  impure  pastes.  If  car- 
bonates are  not  present  calculate  any  calcium  to 
CaSO4+2H2O.  If  carbonates  are  present  deter- 
mine and  calculate  to  whiting,  then  any  remaining 


52  THE  CHEMISTRY  OF  PAINTS 

calcium  to  gypsum.  If  the  absence  of  gypsum  is 
shown  by  the  qualitative  tests,  the  determination 
of  CO2  is  unnecessary  and  the  CaO  present  can  be 
calculated  to  CaCO3  by  the  factor  1.784.  Subtract 
total  adulteration  found  from  100.00  to  determine 
the  percentage  color  present. 

Note.  Mixtures  of  oxides,  ochres,  umbers,  and 
siennas  are  (in  the  absence  of  zinc  and  lead)  an- 
alyzed in  the  same  manner  as  in  umber ',  Chapter 
II,  determining  silica  and  silicates,  Fe2O3,  MnO2, 
H2O,  CaCO3,  etc.  Any  gas  or  lamp  black  is  de- 
termined by  an  appropriate  method  and  expressed 
as  C.  When  chrome  yellow  or  chrome  green  is 
present  the  above  method  may  be  followed.  If  a 
separation  of  the  color  is  desired,  the  precipitate  of 
sulphides  is  dissolved  in  HNO3,  and  lead  separated 
and  determined  in  the  usual  manner.  Mn,  Fe, 
and  Cr  are  determined  in  the  nitrate,  and  Cr  sep- 
arated and  calculated  to  PbCrO4.  Any  remaining 
lead  is  (in  the  absence  of  white  lead)  calculated  to 
PbSO4,  and  any  remaining  sulphate  to  CaSO4  if 
calcium  is  present.  If  no  calcium  is  present  all 
sulphate  is  calculated  to  PbSO4,  the  remaining  lead 
to  PbCrO4,  and  from  this  the  Cr2O3  calculated  and 
subtracted  from  the  total  oxides  of  Mn,  Fe,  and 
Cr,  in  which  case  the  separation  of  chromium  is 
unnecessary. 

i.  a.  With  permanent  red  the  process  is  a  trifle 
different.  In  the  absence  of  china  clay  and  red 
lead  dissolve  in  very  dilute  HC1.  The  barytes  and 


ANALYSIS  OF  PAINTS  53 

red  will  remain  undissolved.  Filter  on  a  Gooch 
crucible.  Dry  in  air  oven  to  constant  weight,  then 
weigh,  ignite,  and  weigh  barytes,  getting  dye  by 
difference.  This  gives  very  good  results  when  the 
acid  used  is  properly  diluted  and  the  digesting  not 
continued  for  too  long  a  time.  When  china  clay  is 
present  (very  rarely  the  case)  the  results  cannot  be 
depended  upon,  as  there  is  a  loss  due  to  the  water 
it  contains.  The  A12O3  must  be  obtained  as  in  S.  I. 
and  china  clay,  the  per  cent  water  estimated,  sub- 
tracted from  the  total  loss  on  ignition,  and  the  re- 
mainder expressed  as  the  amount  of  dye  present. 
This,  however,  will  give  only  approximate  results 
in  many  cases.  If  Pb3O4  is  present  it  will  generate 
Cl  by  acting  on  the  HC1,  and  this  will  have  a  ten- 
dency to  destroy  the  dye  and  lower  the  result.  In 
such  cases  the  dye  must  be  obtained  by  difference 
after  the  other  constituents  have  been  determined 
(or  in  the  absence  of  carbonates  and  combined 
moisture  by  direct  ignition).  This  also  will  generally 
lead  to  an  error  by  giving  too  high  results,  but  by 
taking  an  average  of  the  amount  determined,  and 
that  calculated  by  difference,  a  result  will  generally 
be  obtained  by  which  the  sample  can  be  matched 
correctly.  A  special  discussion  on  this  point  will 
be  found  in  the  matching  of  vermilions.  (See 
page  69.) 

When  red  lead  is  present  without  any  white  lead, 
sublimed  lead,  or  zinc,  determine  as  PbSO4  by  dis- 
solving the  precipitate  of  PbS  in  HNO3  and  treating 


54          THE  CHEMISTRY  OF  PAINTS 

as  in  L.  I.  If  white  lead  and  lead  sulphate  are 
present  but  no  calcium,  determine  CO2  and  SO3 
present,  then  convert  to  white  lead  and  sulphate 
of  lead,  calculating  any  remaining  lead  as  red 
lead.  In  case  whiting  also  is  present  first  satisfy 
it  with  CO2,  calculate  the  remaining  CO2  to  white 
lead,  any  SO3  present  (in  absence  of  gypsum)  to 
PbSO4,  and  the  remaining  lead  to  Pb3O4.  If 
zinc  is  present  it  is  obtained  by  treating  the 
filtrate  from  the  PbSO4  in  the  same  manner  as 
described  under  the  analysis  of  sublimed  lead, 
Chapter  II. 

Such  complications  as  the  above  will  rarely  or 
never  occur,  although  permanent  red  pastes  very 
often  prove  to  be  the  most  complex  mixtures  with 
which  the  paint  chemist  comes  in  contact,  and  often 
to  determine  the  manner  in  which  the  materials 
present  are  combined  is  a  very  difficult  matter. 

In  scarlet  and  eosine  vermilions,  if  a  complete 
analysis  is  desired,  determine  what  dye  is  present  by 
the  table  given  under  Permanent  Reds,  Chapter  II. 
(See  page  29.)  Treat  i  gm.  as  in  dry  colors,  first 
getting  the  adulteration  as  there  described,  but 
vary  the  process  by  dissolving  the  precipitate  of 
PbS  in  concentrated  HNO3  as  in  permanent  reds, 
and  determine  the  lead  present  as  PbSO4  by  L.  I., 
calculating  it  to  Pb3O4.  The  dye  may  then  be 
obtained  by  difference,  which  yields  results  close 
enough  for  purposes  of  matching.  White  lead,  sub- 
limed lead,  or  zinc  occasionally  may  be  found  in 


ANALYSIS  OF  PAINTS  55 

cosine  and  scarlet  vermilions.  In  this  case  treat  as 
above  in  Permanent  Reds.  In  case  of  a  mixture  of 
Pb3O4  and  American  vermilion  determine  total  lead 
as  PbSO4  and  total  chromium  as  Cr2O3.  Multiply 
Cr2O3  by  8.02  and  express  result  as  American  ver- 
milion. Divide  this  result  by  .883  and  subtract  from 
total  PbSO4  found,  calculating  remainder  to  Pb3O4. 
2.  White  and  Tinted  Paints  containing  no  Calcium. 
—  Dissolve  i  gm.  in  dilute  HC1  as  in  i.  Filter,  wash, 
dry,  ignite,  and  weigh  the  insoluble  residue.  The 
residue  may  be  barytes,  china  clay,  or  silicate  of 
magnesium.  (Any  lead  sulphate  which  has  not 
been  completely  dissolved  will  be  shown  here  as  a 
metallic  globule  in  the  bottom  of  the  crucible.) 
Separate  the  residue  by  S.  I.  or  S.  I.  a.  If  china  clay 
is  found  its  combined  water  must  be  calculated  and 
added  to  it  as  explained  under  China  Clay,  Chap- 
ter II.  Add  5  c.c.  concentrated  H2SO4  to  the  fil- 
trate, evaporate  to  concentrated  sulphuric  acid 
fumes  and  determine  lead  as  in  L.  I.,  then  make 
alkaline  with  ammonia  and  boil.  The  precipitate 
may  be  hydroxides  of  Fe,  Cr,  and  Al,  all  com- 
ing from  the  tinters  of  the  paint  (or  A12O3  from 
the  adulterating  materials).  This  precipitate  is 
usually  discarded,  as  the  tinters  are  customarily 
calculated  by  difference,  but  any  chromium  pres- 
ent may  be  determined  at  this  point  by  separating 
as  in  I.  II.,  calculating  to  PbCrO4,  this  being 
calculated  to  PbSO4  and  this  subtracted  from  the 
total  lead  determined  as  PbSO4. 


56  THE  CHEMISTRY  OF  PAINTS 

The  filtrate  now  contains  any  zinc  that  may  be 
present.  Saturate  with  H2S,  boil,  let  settle,  filter. 
If  but  a  small  amount  is  present  and  absolute  re- 
sults are  not  required,  dry,  burn,  let  cool,  add  a 
few  drops  of  concentrated  HNO3,  dry,  and  ignite 
for  the  second  time  at  high  heat,  and  weigh  as 
ZnO.  This  will  give  results  a  trifle  high,  owing  to 
the  fact  that  all  sulphur  cannot  be  removed  by 
burning.  The  error  is  not  large,  however,  pure 
ZnO  showing  101%  zinc  oxide  by  this  method  where 
99.8%  is  shown  when  precipitated  as  carbonate. 
If  the  amount  present  is  large  and  very  accurate 
results  are  desired,  wash  precipitated  ZnS  free  from 
ammonium  salts,  dissolve  in  HC1  and  determine 
zinc  by  Z.  I. 

In  white  paints  the  filtrate  from  the  lead  determi- 
nation should  be  precipitated  directly  with  Na2CO3, 
as  the  absence  of  Cr  and  Fe  is  assured. 

Determine  SO3  on  separate  sample  and  calculate 
to  PbSO4. 

Determine  CO2  on  a  separate  sample  and  calcu- 
late to  white  lead.  Any  lead  not  satisfied  (after 
calculating  any  Cr2O3  formed  to  PbCrO4)  is  cal- 
culated as  PbO. 

3.  White  and  Tinted  Paints  containing  Whiting 
without  Gypsum.  —  Dissolve  in  dilute  HC1  and 
proceed  as  in  method  i,  excepting  that  the  precipi- 
tate of  sulphides  must  be  dissolved  in  concentrated 
HNO3,  washed  thoroughly  until  the  filter  is  free 
from  acid,  then  5  c.c.  concentrated  H2SO4  added 


ANALYSIS  OF  PAINTS  57 

and  the  analysis  continued  as  in  method  2.  Deter- 
mine the  calcium  in  the  filtrate  from  the  precipitate 
of  sulphides,  and  calculate  the  resultant  CaO  to 
CaCO3  by  the  factor  1.784.  Determine  SO3  on  a 
separate  sample  and  calculate  to  PbSO4.  Calculate 
any  lead  not  thus  satisfied  (in  case  of  chrome  yellow 
tints  first  determine  PbCrO4  and  deduct  from  re- 
maining lead)  to  white  lead.  This  will  give  a  result 
on  white  lead  that  is  a  trifle  high,  owing  to  the  pres- 
ence of  oxides  of  lead  in  the  sublime  products  pres- 
ent, but  the  error  will  be  no  greater  than  is  made 
by  determining  the  CO2,  calculating  to  whiting 
and  calculating  the  remainder  to  white  lead,  since 
whiting  is  very  liable  to  contain  lime,  thus  causing 
the  calculated  white  lead  to  be  low.  There  is  as 
much  possibility  of  error  in  one  method  as  in  the 
other  (not  large  enough  to  be  of  importance  in 
either),  and  the  former  is  to  be  preferred  owing  to 
the  fact  that  one  less  determination  is  necessary. 
On  the  whole  the  determination  of  CO2  may  be 
dispensed  with  in  nearly  all  analyses  of  paint  samples 
without  causing  much  error.  Absolute  results  are 
very  seldom  required  and  are  very  seldom  of  im- 
portance, since  in  making  up  a  sample  to  match 
the  analysis  an  approximation  only  is  attempted. 
A  very  close  result  should  always  be  obtained  on 
the  percentage  adulteration,  but  an  error  of  one  or 
two  per  cent  on  any  white  lead,  zinc,  or  sulphate 
of  lead  matters  but  little,  owing  to  the  fact  that 
they  do  not  differ  materially  in  cost. 


58  THE  CHEMISTRY  OF  PAINTS 

4.  When  Whiting,  Sulphate  of  Lead,  White  Lead, 
and  Gypsum  are  present  (a  very  unusual  combina- 
tion).—  Determine  whiting  on  a  separate  sample  by 
Thompson's  method.  Determine  SO3  on  separate 
sample.  Proceed  with  the  analysis  as  in  method 
3.  Calculate  the  remaining  calcium,  not  carbon- 
ate, as  CaSO4+2H2O,  then  the  remaining  SO3 
to  PbSO4,  and  the  remaining  lead  to  white  lead 
if  PbCrO4  is  not  present.  In  case  chromium  is 
present  it  may  be  determined  as  Cr2O3,  then  cal- 
culated first  to  PbCrO4,  this  calculated  to  white 
lead  and  subtracted  from  the  weight  of  white  lead 
previously  obtained.  Or  the  CO2  may  be  deter- 
mined and  whatever  is  left  after  satisfying  the 
CaCO3  may  be  calculated  to  white  lead,  any  Cr2O3 
present  calculated  to  PbCrO4,  and  any  lead  remain- 
ing besides  the  PbSO4  previously  calculated,  ex- 
pressed as  PbO.  This  last  result  will  be  accurate 
only  when  the  whiting  present  contains  no  CaO. 

Note.  Where  great  haste  is  necessary  in  mak- 
ing an  analysis,  variations  of  the  foregoing  methods 
may  be  used.  Lead  may  be  precipitated  alone 
with  H2S  in  slightly  acid  (HC1)  solution,  redis- 
solved  in  HNO3  and  determined  in  the  usual  man- 
ner. Or,  where  only  present  in  small  amounts 
and  no  great  accuracy  is  required,  the  precipitate 
may  be  burned  separate  from  filter  paper,  a  small 
amount  of  HNO3  added,  evaporated  to  dryness, 
the  residue  ignited  strongly  and  weighed  as  PbO. 

This  leaves  all  the  third  and  fourth  group  metals 


ANALYSIS  OF  PAINTS  59 

present  in  solution  (with  small  amounts  of  lead,  if 
the  precipitation  with  H2S  has  not  been  carefully 
performed).  Third-group  metals  are  separated  by 
precipitation  with  ammonia  and  H2S,  leaving 
calcium  present  in  solution.  The  precipitate  is 
dissolved  in  HNO3  or  HC1,  and  iron,  chromium, 
and  aluminium  precipitated  with  NH4OH,  leav- 
ing zinc  in  solution.  This  is  precipitated  and 
determined  by  an  appropriate  method. 

Another  method  is  to  precipitate  lead  and  all 
third-group  metals  with  NH4OH  and  H2S,  redis- 
solve  in  HNO3  determining  lead  as  usual  and  ob- 
taining calcium  in  filtrate.  Zinc  is  obtained 
by  dissolving  the  original  sample  in  a  mixture 
of  alcohol  and  sulphuric  acid.  This  will  leave 
all  lead  behind  as  PbSO4  as  well  as  the 
greater  amount  of  any  calcium  present.  Iron  and 
aluminium  are  precipitated  with  NH4OH,  and  finally 
zinc  by  the  addition  of  H2S,  or  yellow  ammonium 
sulphide. 

Both  these  methods  involve  as  much  or  more 
work  than  former  methods  given,  but  the  necessity 
of  waiting  until  lead  is  determined  before  deter- 
mining third-group  metals  is  avoided  and  consider- 
able time  saved. 

SPECIAL 

5.  Ochre  Tints.  —  Where  ochre  is  used  for  tints 
it  will  remain  behind  with  the  insoluble  impurities 
on  treating  with  acid.  The  fact  that  ochre  has  no 


60          THE  CHEMISTRY  OF  PAINTS 

standard  of  purity  and  is  very  much  the  same  in 
composition  as  china  clay  makes  a  separation  im- 
practical. The  author  has  found  that  the  most 
convenient  method  is  to  digest  the  sample  in  dilute 
HC1  and  treat  the  filtrate  by  any  appropriate 
method  previously  given.  Excepting  for  a  small 
quantity  of  Fe2O3  dissolved,  the  ochre  will  remain 
behind  intact.  Any  barytes  present  is  determined, 
subtracted  from  the  total  insoluble  residue  and  the 
remainder  expressed  as  ochreous  material.  To  this 
must  be  added  10  per  cent  of  its  weight  for  com- 
bined water.  The  sample  is  then  matched  from 
the  analysis  by  method  5,  Chapter  IV. 

6.  Ultramarine  Tints.  —  As  ultramarine  contains 
in  itself  several  materials  used  as  adulterants,  as  well 
as  soluble  silicates,  a  paint  in  which  it  is  used  as  a 
tinter  must  be  analyzed  by  a  special  method. 
Dissolve  i  gm.  in  HC1,  evaporate  on  a  hot  plate 
until  nearly  dry,  then  heat  in  an  air  oven  at  120°  C. 
(not  above)  for  one  hour  after  it  has  become  dry. 
Boil  with  dilute  HC1,  decant  on  filter,  repeat,  and 
finally  wash  the  insoluble  material  until  free  from 
acid.  This  residue  will  contain  all  the  SiO2  in  the 
ultramarine  as  well  as  any  insoluble  adulterants. 
Separate  by  S.  I.  Determine  the  materials  in  the 
filtrate  by  an  appropriate  method.  (Ultramarine 
tints  will  almost  invariably  be  found  free  from  lead, 
excepting  what  exists  as  an  impurity  in  the  zinc 
oxide  used.)  The  percentage  of  ultramarine  may 
be  approximately  determined  by  the  percentage 


ANALYSIS  OF  PAINTS  61 

of  A12O3  in  the  filtrate,  but  the  author  usually  dis- 
regards it  and  matches  sample  by  method  6,  Chap- 
ter IV. 

MIXED  PAINTS 

Determination  of  Pigment.  —  Many  different 
methods  are  in  vogue  to  accomplish  this,  mostly  in- 
volving the  use  of  an  extraction  apparatus.  The 
following  simple  method  is  used  by  the  author  and 
gives  very  fair  results :  — 

Measure  off  25  c.c.  of  the  thoroughly  stirred 
paint  in  a  pipette  and  transfer  to  a  weighed  6-oz. 
beaker.  Wash  the  pipette  thoroughly  with  benzine, 
allowing  the  washings  to  run  into  the  beaker. 
Fill  with  benzine  and  stir  with  a  glass  rod  that  has 
been  weighed  with  the  beaker.  Let  stand  until 
thoroughly  settled,  decanting  into  a  32-oz.  beaker. 
Repeat  washing  with  benzine  until  the  sample  is 
free  from  oil.  (It  is  best  to  wash  four  or  five  times, 
the  number,  of  course,  depending  upon  the  character 
of  the  pigment  and  how  far  it  settles  in  the  beaker.) 
Finally  add  any  pigment  that  may  have  settled  out 
in  the  large  beaker  due  to  decanting  too  soon  or 
to  accident  while  doing  so.  Dry  in  an  oven  until 
free  from  benzine.  When  dry,  weigh  the  rod  with 
the  contents  of  the  beaker,  then  subtract  from 
this  result  the  weight  of  the  beaker  and  rod,  and 
get  grams  pigment  in  25  c.c.  of  paint,  and  from  this 
calculating  the  pounds  of  dry  pigment  per  100 
gallons  paint.  If  it  is  desired  the  solution  con- 
taining the  oil  may  be  evaporated  to  dryness  and 


62 


THE  CHEMISTRY  OF  PAINTS 


the  weight  of  the  oil  determined,  in  which  case  car- 
bon-disulphide  free  from  sulphur  is  best  used  as  a 
solvent  and  the  vapor  condensed  during  evaporation. 
The  washed  sample  may  now  be  taken  for  analysis, 
after  being  thoroughly  mixed  and  pulverized. 

Determination  of  Water,   "  Turps,"  and  Benzine. 
— The  apparatus  used  is  represented    below.     It 


T. 


E. 


t 


H. 


consists  of  a  copper  retort  A,  of  about  200  c.c. 
capacity,  detachable  at  D  to  admit  of  filling  and 
subsequent  cleaning.  G  is  a  small  opening  for 
admission  of  coal  gas.  (This  may  be  dispensed 
with,  but  when  used  it  should  be  freed  from  mois- 
ture by  passing  through  CaCl2.)  The  copper  tube 
leading  from  the  retort  is  connected  at  B  to  the 
glass  condenser  C.  A  copper  oven,  open  at  the 
bottom  excepting  for  a  covering  of  copper  gauze, 
is  fitted  over  the  apparatus  as  shown.  It  contains 


ANALYSIS  OF  PAINTS  63 

a  thermometer  T,  and  is  heated  by  a  Bunsen 
burner  E.  H  is  a  vessel  containing  cold  water,  in 
which  is  immersed  a  10  c.c.  cylinder  graduated 
in  TV  c.c.  for  collecting  the  distillate. 

PROCESS.  —  Measure  off  accurately  in  a  gradu- 
ate 100  c.c.  of  the  thoroughly  stirred  sample  and 
pour  it  into  the  retort.  Let  drain  thoroughly. 
A  small  amount  will  still  remain  in  the  cylinder 
and  should  be  washed  down  with  50  c.c.  benzine 
accurately  measured.  By  subtracting  the  amount 
of  benzine  used  from  the  resultant  liquid  in  the 
measuring  cylinder  the  amount  of  paint  that  re- 
mained may  be  estimated,  and  from  this  the  amount 
of  paint  used  in  the  retort.  Now  connect  the  appa- 
ratus, placing  a  cork  in  G  or,  better,  connecting 
with  a  stream  of  well  dried  coal  gas.  Heat  the  oven 
at  110°  C.  to  120°  C.,  taking  care  that  the  tempera- 
ture does  not  rise  above  this,  until  no  more  distillate 
comes  over.  If  any  water  is  present  it  will  be 
found  in  the  lower  layer,  while  any  benzine  will  be 
found  on  top.  In  case  the  cylinder  becomes  full 
before  all  the  distillate  is  collected,  read  off  the 
respective  volumes  of  each  and  replace  it  by  another 
10  c.c.  cylinder,  collecting  the  remainder,  and  adding 
to  the  previous  amount.  Now  increase  the  temper- 
ature gradually  to  175°  C.,  collecting  any  distillate 
that  may  come  over,  and  keep  at  that  temperature 
until  no  further  distillate  appears.  This  is  read 
off  and  recorded  as  "  turps."  The  c.c.  water,  ben- 
zine, and  "turps"  thus  obtained  are  equivalent  to 


64  THE  CHEMISTRY  OF  PAINTS 

the  same  number  of  gallons  in  the  number  of  gallons 
of  paint  equal  to  the  c.c.  paint  taken.  Calculate  to 
gallons,  water,  "turps,"  and  benzine  in  100  gallons 
of  paint. 

The  above  results  will  always  be  found  low.  In 
case  turpentine  is  present  in  considerable  quantity 
the  vapor  from  it  will  drive  off  practically  all  the 
water  and  benzine,  but  not  all  of  the  turpentine  it- 
self will  distil  over.  If  desired  the  water,  "turps" 
and  benzine  may  be  distilled  together  at  the  high 
temperature  (175°  C.  to  185°  C.).  The  volume  of 
water  may  then  be  read  off  and  partly  separated 
from  the  "turps"  and  benzine  by  a  glass-stoppered 
separatory  funnel  and  finally  completely  removed 
by  shaking  the  residue  in  the  funnel  with  well  dried 
calcium  chloride.  The  ratio  of  "turps"  and  ben- 
zine may  now  be  determined  as  described  under 
Turpentine  in  Chapter  V. 

The  following  apparatus  and  method  is  recom- 
mended by  George  H.  Ellis,  who  has  used  it  satis- 
factorily for  several  years. 

The  apparatus  consists  of  a  copper  cylinder 
detachable  at  the  top  and  with  an  opening  at  the 
bottom  covered  with  copper  gauze.  This  is  clamped 
to  an  upright  support  and  contains  an  Erling- 
myer  flask  supported  from  the  top,  fitted  with  an 
entrance  tube  for  gas  and  connected  with  the  con- 
denser. A  thermometer  is  inserted  in  the  copper 
cylinder.  The  gas  passing  through  the  apparatus 
is  allowed  to  pass  out  of  the  graduate  and  is  then 


ANALYSIS  OF  PAINTS  65 

burned.      Its  flow  is  regulated  by  means  of  a  small 
stopcock  in  the  glass  Y. 

Twenty-five  to  fifty  grams  of  the  paint  or  var- 
nish are  weighed  out  and  mixed  with  sufficient  thor- 
oughly dried  sublimed  lead  to  make  a  dry  powder. 
This  is  placed  in  the  flask  by  means  of  a  funnel 
made  from  glazed  paper,  the  apparatus  connected, 
and  the  distillation  proceeded  with  as  in  the  former 


method.  By  this  means  the  volatile  portion  seems 
to  distil  more  readily,  and  after  completing  the 
determination  the  flask  is  more  easily  cleaned.  The 
graduate  is  weighed,  and  when  all  water  and  ben- 
zine have  distilled  over,  the  graduate  and  contents 
are  weighed  and  the  increase  in  weight  equals  water 
and  benzine.  The  weight  of  water  in  grams  is  equal 
to  the  c.c.  present,  and  the  difference  equals  benzine. 
The  temperature  is  now  increased  to  175°  C.,  all 
turpentine  collected  and  determined  by  the  further 


66          THE  CHEMISTRY  OF  PAINTS 

increase  in  weight.  From  the  weight  of  paint  taken, 
the  percentage  by  weight  of  water,  turpentine,  and 
benzine  can  be  readily  calculated. 

It  will  be  observed  that  this  method  gives  the 
percentage  thinners  by  weight  and  not  by  volume,  as 
does  the  former  method.  In  the  author's  opinion 
this  is  not  so  convenient  and  it  requires  more  time 
to  weigh  the  sample  than  to  measure  it.  If  desired, 
the  method  of  measuring  the  liquid  can  be  used 
instead  and  the  volume  percentage  thus  obtained. 

Note  i.  When  manganese  is  present  in  tinted 
paints  it  will  be  precipitated  with  zinc  by  the 
methods  given,  but  it  would  hardly  be  present  in 
quantities  sufficient  to  have  any  appreciable  effect 
on  the  results  for  ZnO. 

Note  2.  When  it  is  desired  to  obtain  Cr2O3  in 
a  tinted  paint  containing  PbCrO4,  it  should  be 
determined  on  a  separate  sample  of  10  to  20  gms. 
according  to  the  quantity  present.  Digest  with  an 
excess  of  dilute  HNO3  and  alcohol  until  all  the 
chromate  is  dissolved  and  reduced  to  the  chromic 
salt.  Add  sufficient  H2SO4  to  precipitate  all  lead 
present,  separate  in  the  usual  manner,  precipitate 
Cr  in  the  filtrate  with  NH4C1  and  NH4OH,  and 
separate  from  any  iron  present  by  I.  II. 


CHAPTER  IV 
THE  MATCHING   OF   SAMPLES 

Dry  Colors. —  In  order  to  properly  match 
samples  of  dry  colors,  and  supply  materials  accord- 
ing to  the  sample,  a  very  large  line  of  colors  is  neces- 
sary with  the  proper  facilities  for  mixing.  Colors 
of  the  same  shade  should  be  at  hand  containing 
various  percentages  of  adulteration,  in  addition  to 
the  pure  colors.  The  exact  percentage  of  im- 
purities, and  the  kind,  should  be  known  in  all 
cases.  To  make  a  special  color  by  precipitation  for 
every  sample  submitted  is  out  of  the  question,  and 
can  only  be  attempted  where  a  large  contract  is  to 
be  filled. 

The  chemist  should  get  approximately  the  per- 
centage of  the  materials  needed  to  closely  match  the 
sample  in  shade  and  composition.  A  small  mix 
should  then  be  made  and  ground  on  sample  mill. 
If  the  shade  is  not  correct  the  formula  is  varied 
and  different  mixes  made  until  the  desired  shade 
is  produced,  always  varying  the  materials  in  such  a 
way  as  to  keep  the  percentage  adulteration  and  the 
kind  of  adulterating  materials  the  same.  Adding 
the  straight  adulteration  to  reduce  the  material  to 
the  same  grade  as  the  sample  should  be  avoided  when- 
ever possible.  A  strength  test  is  then  made  between 

67 


68  THE  CHEMISTRY  OF  PAINTS 

the  material  thus  produced  and  the  sample,  in 
order  to  check  results.  The  strength  of  pure 
greens,  yellows,  and  blues  of  different  makes  will, 
in  most  cases,  be  found  to  be  the  same.  A  c.p. 
chrome  yellow  is  now  on  the  market,  however,  which 
is  fully  40  per  cent  stronger  than  the  average  pure 
chrome  yellow,  and  it  is  obvious  that  a  green  made 
from  this  material  would  also  have  extra  strength. 
A  discrepancy  would  then  be  shown  in  this  case 
between  the  analysis  and  strength  test,  and  under 
such  conditions  the  color  should  be  matched  ac- 
cording to  strength.  Pure  blues  will  be  found  to 
vary  but  little  in  strength  (i.e.,  Chinese  from 
Chinese,  and  Prussian  from  Prussian  —  Chinese 
is  a  much  stronger  color  than  Prussian)  and  are 
best  matched  by  strength  alone,  the  shade  in  oil 
and  the  tint  always  being  taken  into  consideration. 

Where  a  dry  color  is  to  be  used  for  tinting  this 
fact  should  be  taken  into  consideration  and  the  tint 
matched.  It  is  not  usually  necessary  to  match 
the  sample  dry  as  well  as  in  oil,  unless  the  color  is 
to  be  used  as  a  distemper  color. 

i.  a.  VERMILIONS,  EOSINE  AND  SCARLET.  —  Owing 
to  the  wide  variation  in  the  strength  of  red  leads 
and  orange  minerals  the  strength  of  the  resultant 
vermilions  also  varies  through  wide  limits,  and  in 
matching  a  vermilion,  whether  dry  or  in  oil,  this 
fact  must  always  be  taken  into  consideration. 
The  shade  in  oil  will  generally  give  some  idea  of 
the  grade  of  the  lead  in  the  vermilion,  but  not 


MATCHING  OF  SAMPLES  69 

always.  The  bulk  is  also  of  great  importance. 
The  first  thing  to  do  in  matching  a  sample  of  ver- 
milion is  to  match  the  shade  in  oil.  Then  make 
a  small  sample  with  the  same  percentage  Pb3O4 
and  adulteration  as  the  sample  to  be  matched,  and 
try  the  strength.  To  be  a  proper  match  the  strength 
should  be  the  same.  If  not,  changes  must  be 
made  until  this  is  accomplished.  It  sometimes 
occurs  that  the  color  cannot  be  matched  in  shade 
and  composition  as  found  by  analysis  and  the 
same  strength  obtained.  In  this  case  the  adultera- 
tion should  be  varied  from  that  shown  by  analysis 
until  the  desired  strength  is  produced.  To  properly 
match  dry  vermilions  a  large  line  of  vermilions  of 
different  grades  and  purity  is  necessary,  and  with- 
out these  satisfactory  results  cannot  be  obtained. 

i.  b.  PERMANENT  REDS,  DRY  AND  PASTE.  —  Per- 
manent reds  may  usually  be  matched  from  the  analy- 
sis, but  where  they  contain  red  lead  this  cannot 
easily  be  done.  If  the  chemist  has  on  hand  perma- 
nent reds  containing  known  percentages  of  dye,  red 
lead,  orange  minerals,  etc.,  he  can  match  them  in 
much  the  same  manner  as  in  other  vermilions, 
seeking  that  combination  which  will  give  him  the 
proper  shade  in  oil  and  strength,  and  conform  to 
the  analysis  of  the  sample.  Complications  arise, 
however,  owing  to  the  difference  in  character  and 
properties  between  the  coloring  matter  produced 
by  the  addition  of  diazotized  para  nitranaline  and 
beta  naphthol  and  the  darker  shade  produced  by  the 


70  THE  CHEMISTRY  OF  PAINTS 

additional  presence  of  mono-sulphonic  acid.  The 
latter  will  show  the  same  as  the  former  in  analysis, 
but  is  stronger  and  has  a  bluer  undertone. 

Whenever  possible  it  will  be  found  advisable  and 
more  economical  to  match  samples  of  permanent 
red  in  oil  containing  orange  mineral,  by  using  the 
pure  toner  in  the  proportion  found  by  analysis, 
grinding  with  it  the  orange  mineral  and  other 
materials  found  present.  If  the  orange  mineral 
used  has  the  proper  strength  and  the  toner  is  of  the 
proper  character  the  resultant  shade  should  have 
the  same  depth  of  color  as  the  sample.  Otherwise 
different  grades  of  orange  mineral  should  be  tried 
until  one  is  found  which  gives  the  proper  results. 

2.  Untinted  Colors  in  Oil,  Japan,  and  Varnish.  — 
It  is  first  necessary  to  get  some  idea  of  the  vehicle 
in  which  the  material  is  ground.  To  determine 
the  grade  of  the  vehicle  used  by  chemical  tests  is 
impossible,  but  by  simple  tests  a  fairly  accurate 
idea  may  be  gained.  Only  wide  experience,  how- 
ever, will  make  one  competent  to  do  this.  The 
colors  should  be  spread  out  thin  on  glass,  and  its 
time  of  drying  noted,  also  the  way  in  which  it  dries ; 
its  odor,  hardness,  etc.  The  manner  in  which 
japan  and  varnish  colors  spread  is  important. 

The  grade  of  pigment  must  also  be  taken  into 
consideration,  as  it  is  very  unusual  to  grind  cheap 
colors  in  expensive  vehicles,  and  vice  versa.  Corn, 
cottonseed,  and  mineral  oils  when  present  in  any 
considerable  quantities  can  often  be  detected  by 


MATCHING  OF  SAMPLES  71 

the  odor.  When  a  deodorizer  such  as  oil  of  myr- 
bane  is  present  one  can  always  be  certain  that  some 
adulterating  oil  is  present  in  large  quantities. 
Pastes  are  often  ground  in  a  mixture  of  benzine 
and  oil,  in  which  case  the  paste  will  dry  flat  without 
the  smoothness  and  hardness  of  a  japan  color, 
and  the  benzine  can  be  determined  by  drying  a 
weighed  portion  of  the  sample  at  100°  to  110°  to 
constant  weight.  The  chemist  should  try  pastes 
made  up  with  different  vehicles  at  hand,  note  their 
properties  and  try  different  mixtures  until  he  be- 
comes thoroughly  acquainted  with  the  action  of  all 
vehicles  at  hand.  With  practice  mixtures  of  oil 
and  japan,  oil  and  varnish,  japan  and  varnish,  etc., 
can  be  readily  distinguished.  The  paste  which  is 
to  be  furnished  should  be  so  made  as  to  be  like  the 
sample  in  drying,  gloss,  odor,  and  all  other  physical 
properties.  The  proper  matching  of  the  vehicle  is 
as  important  as  the  proper  matching  of  the  pigment, 
and  should  be  done  with  the  greatest  of  care. 

The  colors  should  be  matched  on  glass  ground  in 
the  proper  vehicle,  using  pure  colors  whenever 
possible,  adding  the  adulteration  in  the  proportion 
found  by  analysis.  In  the  case  of  japan  colors  the 
sample  thus  made  and  the  sample  to  be  matched 
should  be  allowed  to  dry  thoroughly  side  by  side 
on  glass,  and  then  varnished  over  to  be  certain  that 
the  shade  is  correct.  It  will  be  found  cheaper  to 
use  the  c.p.  colors  and  add  the  adulteration  when 
mixing  than  to  use  colors  which  have  been  adul- 


72  THE  CHEMISTRY  OF  PAINTS 

terated  in  making;  but  oftentimes  the  proper  shade 
cannot  be  produced  by  the  former  method,  owing 
to  the  fact  that  the  adulteration  when  mixed  will 
flat  more  than  when  made  in  the  color.  Match  ver- 
milion pastes  as  given  under  Vermilion  Dry  Colors. 

3.  White  and  Tinted  Pastes. —  Take  the  zinc, 
sulphate  of  lead,  and  white  lead,  whiting,  etc.,  in 
the  proportions  found  in  the  sample,  and  tint  to 
shade  with  pure  colors  whenever  possible.     In  case 
impure  tinters  are  used,  such  as  umbers,  oxides, 
etc.,  the  amount  of  foreign  matter  in  these  must  be 
calculated  and  a  corresponding  amount  subtracted 
from  the  adulteration  to  be  added.     On  this  account 
it  is  imperative  that  the  percentage  purity  of  all 
stock  materials  be  known. 

4.  White  and  Tinted  Paints.  —  Make  up  paste 
as   in   3    to    match    shade    of    mixed    paint,   but 
make  a   trifle   darker    as    the  shade  will   become 
lighter  on  thinning.     On  the  whole  it  will  be  found 
more  rapid  and  convenient  to  grind  together  in 
proper  proportions  all  materials  found  by  analysis, 
excepting  tinters  which  are  added  afterwards  in 
liquid  form  to  the  proper  shade.     In  either  case 
any  adulteration  in  the  tinters  must  be  taken  into 
consideration,  as  in  3.     It  is  best  to  make  up  about 
a  quart  sample  first.     Reduce  pounds  of  dry  pig- 
ment found  per  100  gallons  to  ounce  per  quart, 
and  gallons  water,  benzine,  and  turps  to  fractions 
gallons  per  quart.     Now  weigh  out  such  a  pro- 
portion of  paste  as  will  give  the  proper  ounces  dry 


MATCHING  OF  SAMPLES  73 

pigment  per  quart  as  found,  add  to  this  the  proper 
amount  of  water,  turps,  and  benzine  (also  enough 
drier  to  make  paint  dry  as  does  sample,  deducing 
thinners  in  this  from  benzine  and  turps  to  be  added) 
as  found,  and  make  up  to  volume  with  oil,  or  in 
case  oil  has  been  determined  direct,  add  first  in  the 
proportion  found.  In  case  no  water  is  present 
the  resultant  paint  should  have  the  same  consist- 
ency as  the  sample. 

If  water  is  present  it  may  be  too  thick  or  too 
thin,  showing  that  there  was  too  much  or  too  little 
alkali  in  the  water  used.  In  this  case  the  strength 
of  the  water  solution  must  be  varied  until  the  proper 
consistency  is  obtained. 

The  proper  oil  to  use  offers  a  very  difficult  prob- 
lem. Some  idea  of  it  may  be  gained  by  noting  the 
way  the  paint  dries,  and  by  extracting  some  of  the 
oil  with  chloroform  or  ether,  and  examining  accord- 
ing to  Chapter  V.  This  will  give  but  little  satis- 
faction in  many  cases,  however,  owing  to  the  pres- 
ence of  drier,  etc. ;  but  here,  as  in  paste  goods,  it  will 
almost  invariably  be  found  that  paints  containing 
cheap  pigments  will  contain  cheap  oil.  Usually  a 
considerable  amount  of  corn  or  cottonseed  oil  is 
used  when  price  permits.  In  second-grade  paints 
gloss  oil  will  often  be  present  in  considerable  pro- 
portions. 

In  making  a  mixed  paint  where  good  results  are 
desired  the  presence  of  water  should  best  be  avoided. 
As  alkali  or  some  other  material,  such  as  bleaching 


74  THE  CHEMISTRY  OF  PAINTS 

powder,  must  always  be  added  with  it,  a  certain 
amount  of  oil  is  destroyed  and  a  larger  amount  of 
soluble  material  formed.  If  gloss  oil  (or  a  drier  that 
contains  rosin)  and  sublimed  products  accompany  it, 
the  paint  will  thicken  much  more  rapidly  than  it 
would  otherwise  do,  so  that  after  a  few  months  it 
will  be  found  to  be  unusable.  The  practice  of 
mixing  gloss  oil  with  sublimed  products  (except 
possibly  the  highest  grade  of  zinc)  is  dangerous  at 
the  best,  and  where  water  is  used  is  certain  to  result 
disastrously. 

5.  Yellow  Ochre  Tints.  —  First  take  the  proper 
proportions  of  materials  as  found  by  analysis,  ex- 
cepting the  ochreous  materials,  then  tint  to  shade 
with  yellow   ochre.     If  the   amount   of  ochre  re- 
quired is  not  as  great  as  found  by  analysis,  make 
up  by  the  addition  of  china  clay.     It  will  occasion- 
ally be  found  that  since  the  ochre  used  in  the  sample 
is  unusually  strong,  more  ochre  must  be  used  in 
matching  it  than  the  analysis  shows. 

6.  Ultramarine    Tints.  —  As    stated    under    the 
analysis  of  ultramarine  tints,  complications  often 
arise  owing  to  the  fact  that  the  ultramarine  itself 
contains  materials  essential  to  its  composition  that 
are  often  used  for  adulteration.     Under  ordinary 
circumstances    the    ultramarine   may   be   approxi- 
mated from  the  per  cent  of  A12O3  and  SiO2  present, 
but  in  the  case  of  free  SiO2  and  silicates  the  analysis 
becomes    complicated   and   the   following   method 
should  be  used  in  matching:  — 


MATCHING  OF  SAMPLES  75 

Take  the  white  body  pigments  (i.e.,  zinc  and  lead 
compounds),  together  with  any  barytes,  whiting, 
etc.,  in  the  proportion  found  by  analysis,  and  tint 
to  shade  with  ultramarine.  In  case  this  does  not 
make  a  total  of  100,  add  adulteration  (silica  or 
china  clay)  until  such  is  the  case. 


CHAPTER  V 

PAINT  VEHICLES 

I.    OILS 

The  oils  used  to  any  great  extent  in  the  manufac- 
ture of  paints  are  linseed  (raw,  boiled,  and  bleached), 
cottonseed,  corn,  and  the  so-called  mineral  and  rosin 
oils.  China  wood  oil,  although  now  used  extensively 
in  the  manufacture  of  varnish,  has  made  no  head- 
way in  paints,  owing  to  the  fact  that  without  proper 
treatment  it  will  dry  "flat"  or  dead  and  cause  the 
same  result  when  present  in  any  appreciable  quan- 
tity in  other  oils  or  vehicles. 

Menhaden  oil  is  restricted  by  its  fishy  odor, 
which  has  long  kept  it  from  taking  its  proper  im- 
portant place  in  paint  manufacturing.  It  has  been 
used  to  some  small  extent  for  painting  where  much 
friction  is  improbable,  and  the  author  is  informed 
on  the  best  of  authority  that  it  has  shown  itself 
equal  or  superior  to  linseed  in  wearing  properties. 

The  problem  of  oil  analysis  is  one  which  has 
been  worked  on  extensively,  but  only  with  a  limited 
degree  of  success.  The  author  is  of  the  opinion 
that  a  vast  number  of  tests  suggested  are  worthless. 
It  would  seem  that  the  many  discrepancies  among 
authorities  as  to  the  characteristics  of  different  oils 
can  only  be  accounted  for  by  assuming  that  some 

76 


PAINT  VEHICLES  77 

have  worked  with  impure  oils  or  with  oils  in  dif- 
ferent conditions.  For  instance,  results  obtained 
by  experimenting  on  raw,  bleached,  and  fatty  lin- 
seed would  be  very  different,  although  the  oil  may 
be  correctly  called  linseed  oil  in  each  case.  Owing 
to  the  unsettled  nature  of  our  present  analytical 
knowledge  of  oils  the  chemist  should  be  careful  in 
accepting  tests  without  first  determining  their 
reliability  by  experiments  performed  on  samples 
of  known  purity.  The  few  tests  given  below  are 
carefully  selected  and  are  among  the  most  reliable 
in  use,  but  nevertheless  should  be  checked  against 
samples  of  known  content  if  used  for  the  first  time. 

SPECIAL  TESTS 

i.  Iodine  Number,  (a)  Hiibl  Method. — 0.2  gms. 
oil  or  0.4  gms.  solid  fat  are  dissolved  in  10  c.c.  chloro- 
form in  a  stoppered  flask,  and  20  c.c.  iodine  solution 
added.  This  is  made  by  dissolving  25  gms.  I  in 
i  liter  alcohol,  and  30  gms.  mercuric  chloride  in 
J  liter  of  alcohol,  the  two  solutions  mixed,  allowed 
to  stand  twelve  hours,  and  then  standardized  with 
n/io  Na2S2O3  (see  C.  V.).  After  the  mixture  of 
iodine  and  oil  has  stood  for  eight  hours,  transfer 
to  a  beaker,  rinse  flask  with  KI  solution,  add  150 
c.c.  H2O,  and  if  the  solution  is  not  clear  add  more 
KI  until  such  is  the  case.  Determine  the  excess  of 
I  by  n/io  Na2S2O3  as  in  C.  V.,  and  calculate  I  ab- 
sorbed by  100  gms.  oil  or  fat.  For  interpretation  of 
results  see  Table  IV,  Appendix. 


78  THE  CHEMISTRY  OF  PAINTS 

The  iodine  solution  changes  strength  very  rapidly. 
It  should  always  be  restandardized  immediately  be- 
fore using  and  an  additional  amount  added  to  the 
oil  solution  to  make  up  for  the  loss  in  strength. 
The  iodine  must  always  be  kept  in  considerable 
excess  or  results  will  be  obtained  which  are  entirely 
unreliable.  Keep  the  solution  tightly  stoppered 
in  a  cool,  dark  place. 

(b)  Wijs  Method. — The  variation  of  this  method, 
known  as  the  Wijs  method,  gives  an  iodine  solution 
which  is  much  more  stable  than  the  Hiibl  solution 
and  acts  with  much  greater  rapidity.  Thirteen  gms. 
of  pure  iodine  are  dissolved  in  a  liter  of  99  per  cent 
c.p.  acetic  acid  and  the  strength  determined  with 
standard  sodium  thio-sulphate.  Chlorine  gas  free 
from  HC1  is  then  passed  into  the  solution  until  it 
oxidizes  twice  as  much  thio-sulphate.  The  proper 
ending  of  the  chlorination  may  be  ascertained  by 
the  change  of  color  from  dark  brown  to  light  yellow. 
If  the  gas  is  passed  in  until  this  just  occurs  the  first 
titration  may  be  dispensed  with.  The  determina- 
tion of  the  iodine  number  is  now  carried  on  in 
exactly  the  same  manner  as  in  the  Hiibl  method, 
with  the  exception  that  the  time  required  for  ab- 
sorption is  greatly  lessened.  When  small  quantities 
of  fat  having  a  low  iodine  value  are  used  the  action 
is  complete  in  less  than  five  minutes,  and  with  fats 
of  higher  values  no  more  than  ten  minutes  are 
required. 

Lewkowitsch  states  that  when  c.p.  99  per  cent 


PAINT  VEHICLES  79 

acid  is  used  the  solution  remains  permanent  for 
two  months,  but  varies  considerably  when  95  per 
cent  acid  is  used. 

2.  Saponification  Number.  — The  following,  known 
as  the  Leffmann-Beam  method,  is  highly  recom- 
mended and  may  be  used  with  more  certainty  of 
complete  saponification  than  any  other  method  now 
in  use.  When  the  presence  of  mineral  oil  is  known 
in  any  vegetable  oil  the  saponification  number 
gives  a  very  good  basis  for  estimating  it  quantita- 
tively. It  also  has  been  recommended  for  the 
quantitative  estimation  of  rosin  and  rosin  oil,  but 
will  be  found  unsatisfactory  for  this  purpose  since 
both  of  these  substances,  rosin  in  particular,  take 
up  a  certain  amount  of  alkali.  Linseed,  corn, 
cottonseed,  china  wood,  and  menhaden  oil,  all  have 
practically  the  same  saponification  number,  i.e.,  re- 
quire the  same  amount  of  alkali  to  change  to  a  soap. 
They  are  ethereal  salts  of  fatty  acids  and  are  decom- 
posed by  caustic  soda  in  practically  the  same  manner 
as  are  the  salts  of  most  metals  with  the  formation 
of  the  soap,  a  sodium  salt  of  the  fatty  acids  present, 
and  glycerine,  a  hydroxide.  As  petroleum  products 
are  hydrocarbons  of  entirely  different  composition 
and  unaffected  by  alkali,  it  will  be  at  once  seen  that 
their  presence  in  any  of  the  above  oils  will  lower 
their  saponification  number,  or  mgms.  KOH  neces- 
sary to  saponify  i  gram,  in  a  direct  ratio  to  the 
amount  present. 

GLYCERINE- SODA  SOLUTION. — Add  20  c.c.  of  a  50 


8o          THE  CHEMISTRY  OF  PAINTS 

per  cent  solution  of  NaOH  to  150  c.c.  of  pure  con- 
centrated glycerine.  The  soda  must  be  as  free 
from  carbonates  as  possible 

Method:  Measure  out  20  c.c.  glycerine-soda 
solution  and  weigh.  Make  up  to  250  c.c.  with 
alcohol  and  titrate  with  decinormal  oxalic  acid 
solution  made  by  dissolving  6.3024  gms.  c.p.  oxalic 
acid  in  i  liter  of  water.  This  may  be  checked 
against  a  standard  alkali  solution  to  make  certain 
that  it  is  correct. 

The  strength  of  the  glycerine-soda  solution  hav- 
ing been  established  in  grams  KOH  per  i  gm. 
solution,  weigh  out  about  25  gms.  in  the  saponi- 
fication  flask.  Weigh  the  flask  containing  the  oil 
to  be  tested  and  add  about  5  c.c.  to  the  glycerine- 
soda  solution,  and  again  weigh  the  flask  containing 
the  oil,  obtaining  the  weight  of  sample  used  by 
difference.  The  saponification  flask  is  now  heated 
until  complete  saponification  takes  place,  care  being 
taken  that  the  heat  is  not  sufficient  to  decompose 
the  glycerine,  which  can  be  observed  by  the  odor  of 
acrolein.  Complete  saponification  should  take  place 
in  less  than  five  minutes  (unless  unsaponifiable 
materials  are  present)  as  evidenced  by  the  mixture 
becoming  perfectly  clear.  Dissolve  the  soap  in 
alcohol.  Make  up  to  250  c.c.  and  titrate  excess  of 
KOH  with  oxalic  acid.  Subtract  this  from  total 
KOH  used  in  the  glycerine-soda  solution  taken,  and 
calculate  mgms.  KOH  necessary  to  saponify  i  gm. 
oil.  (See  Table  IV,  Appendix.) 


PAINT  VEHICLES  81 

3.  Flash  Test.  —  This  test  may  be  performed  in 
any  flash  test  apparatus  at  the  operator's  command, 
and  will  be  found  very  valuable  in  establishing  the 
purity  of  linseed  oil.  It  will  be  found  safer  to  test 
oils  of  known  purity  in  whatever  apparatus  is  used, 
and  keep  the  results  thus  obtained  as  a  check  rather 
than  to  rely  on  tables  given  by  others.  In  making 
the  flash  test  it  should  always  be  the  aim  of  the 
operator  to  keep  the  conditions  as  nearly  constant 
in  all  cases  as  possible.  The  temperature  should 
be  increased  about  5°  C.  to  10°  C.  per  minute,  the 
test  flame  being  applied  at  each  5°  rise.  The  heat 
must  not  be  concentrated  over  too  small  an  area  of 
the  bottom  of  the  cup,  as  this  may  give  rise  to  bub- 
bling of  the  oil,  which  will  cause  small  particles  of 
it  to  be  thrown  from  the  surface  where  the  open 
tester  is  used.  These  particles  will  burn  on  coming 
in  contact  with  the  test  flame  and  may  be  mistaken 
for  the  flashing  point.  The  test  flame  should  be 
very  small  and  always  applied  in  the  same  place; 
same  quantity  of  oil  should  always  be  used,  and 
draughts  avoided.  The  flashing  point  will  be 
noted  by  the  appearance  of  a  slight  bluish  flame, 
accompanied  by  a  faint  explosion  when  the  test  flame 
is  applied.  In  the  case  of  the  open  tester  this 
flame  appears  around  the  sides  of  the  container. 

The  following  results  were  obtained  by  the 
author  with  an  apparatus  consisting  of  a  copper  cup 
heated  by  a  Chaddock  burner,  which  will  be  found 
very  satisfactory. 


82  THE  CHEMISTRY  OF  PAINTS 

OIL  FLASHING   POINT  °C. 

Linseed,  raw 295° 

Linseed,  boiled  (fire  boiled  with  Mn 

and  Pb  driers) 275° 

China  Wood 280° 

Corn    245°-249° 

Crude  Cottonseed 238° 

Summer  Y  Cottonseed 360° 

Winter  Strained  Menhaden  Dark 252° 

light  body 80° 

Rosin  .  medium  body  100° 

heavy  body 140° 

Penn.  white  neutral  sp.  gr.  .857 156° 


5%  neutral  sp.  gr.  .857 
95%  raw  oil  ]  " 


The  flashing  point  of  vegetable  oils  seems  to  vary 
considerably  on  aging.  Before  declaring  a  sample 
of  linseed  oil  adulterated  because  of  a  low  flashing 
point  it  should  be  remembered  that  very  small 
quantities  of  benzine,  kerosene,  and  turpentine 
will  decrease  the  flashing  point  many  degrees,  and 
it  must  be  decided  whether  the  adulteration  is 
present  in  large  enough  quantities  to  show  inten- 
tional adulteration,  or  whether  it  is  due  to  the  use 
of  unclean  barrels  which  may  have  contained  small 
amounts  of  any  of  these  three  substances. 

4.  Sulphuric  Acid  Test.  —  The  bleaching  of  raw 


PAINT  VEHICLES  83 

oil  by  sulphuric  acid  and  steam  is  one  of  the  most 
widely  used  methods  of  preparing  bleached  oils. 
Crude  cotton,  fish,  and  rosin  oils  are  darkened  by 
sulphuric,  and  the  author  has  adapted  the  following 
method  to  determine  their  presence  in  linseed: — 

To  100  c.c.  sample  oil  add  J  c.c.  H2SO4,  66°  B. 
Stir  thoroughly,  finally  removing  the  gummy  matter 
that  collects  on  the  end  of  the  stirring  rod.  A 
sample  of  raw  linseed  of  known  purity  should  be 
treated  in  like  manner.  After  settling  thoroughly 
(over  night  or  longer)  the  pure  linseed  will  be  found 
to  be  about  the  same  in  color  as  before  treatment 
(boiling  with  steam  necessary  to  bleach),  while  an 
oil  containing  5  per  cent  rosin  oil,  10  per  cent  crude 
cotton  or  menhaden,  and  over  20  per  cent  corn  and 
refined  cotton,  will  be  considerably  darker,  increas- 
ing with  the  amount  of  impurities  present.  The 
addition  of  sulphuric  acid  makes  the  odor  of  rosin 
oil  very  noticeable  when  present  in  quantities  as 
small  as  5  per  cent,  while  another  peculiarity  when 
15  to  20  per  cent  or  over  of  any  adulteration  is 
present  is  the  very  marked  decrease  in  the  amount 
of  gummy  matter  collecting  on  the  end  of  the  stir- 
ring rod. 

5.  Taste  and  Odor.  —  The  taste  of  an  oil  is  often 
of  great  value  in  determining  what  impurities  may 
be  present;  also  the  odor  developed  on  heating. 
With  practice,  the  presence  of  foreign  oils  in  raw 
linseed  should  be  identified  by  taste  when  present 
in  the  following  amounts: — 


84  THE  CHEMISTRY  OF  PAINTS 


o     corn. 
i5%-20%  refined  cottonseed. 
io%-i5%  crude  cottonseed. 

5%-io%  menhaden,  crude  and  refined. 

5%-rosin  oil. 

5%-neutral  oil. 

6.  Test  for  Rosin.  —  The  presence  of  rosin  in 
quantities  as  small  as  5  per  cent  can  be  determined 
by  the  Liebermann-Storch  reaction.     This  may  be 
performed  by  placing  two  drops  of  the  oil  to  be  tested 
on  a  watch  glass  placed  on  a  white  paper.    Two  or 
three  drops  of  acid  acetic  anhydride  are  then  added, 
the  mixture  is  stirred  and  a  drop  of  concentrated 
sulphuric  acid  added,   when,  in  the  presence  of 
rosin,  a  purple  coloration  will  form  on  the  edge  of 
the    mixture,    and    quickly    disappear.     This    test 
should  be   applied  to  pure   linseed   oil   to   which 
known  amounts  of  rosin  have  been  added  so  as  to 
familiarize  the   operator  with   the    reaction.     The 
only  other  material  (a  constituent  of  some  animal 
fats)  which  produces  this  color  will  never  be  found 
in  paint  oils,  and  the  appearance  of  this  coloration 
can  be  relied  upon  as  showing  the  presence  of  rosin. 

Regardless  of  many  statements  to  the  contrary 
this  method  as  above  performed,  or  any  variation  of 
it,  cannot  be  used  for  the  detection  of  rosin  oil  or 
rosin  spirits  when  a  reddish  coloration  is  produced, 
which  is  not  at  all  characteristic. 

7.  Halphen's  Test  for  Cottonseed  Oil.  —  5  c.c.  oil 


PAINT  VEHICLES  85 

to  be  tested  are  placed  in  a  test  tube  together  with 
5  c.c.  amyl  acetate  and  5  c.c.  carbon  disulphide 
containing  2  per  cent  of  sulphur  in  solution.  The 
tube  is  heated  for  fifteen  minutes  in  a  parafine  bath 
at  no°C.  The  presence  of  cottonseed  oil  is  in- 
dicated by  the  appearance  of  a  pink  color,  becoming 
more  intense  with  the  amount  present.  Cottonseed 
oil  which  has  been  heated  to  245°  C.-2650  C.  will 
not  respond  to  this  test,  but  such  treatment  would 
hardly  be  given  an  oil  used  to  adulterate  linseed. 

(A)    DRYING  OILS 

Linseed  Oil,  Raw.  —  Per  cent  oil  in  seed,  38-40. 
Constants:  Sp.  gr.  at  15°  C.,  .93I5-.935-  Flashing 
point,  295°  C.  Iodine  number,  172.  Saponifica- 
tion  number,  192. 

Linseed  oil  is  obtained  from  the  seed  of  the  flax 
plant  by  extraction  or  subjection  to  hydraulic  pres- 
sure. The  cold  pressed  is  thicker  and  lighter  in 
color  and  has  a  higher  iodine  and  saponification 
number  than  has  the  warm  pressed  whose  constants 
are  given  above.  Warm  pressed  oil  is  golden 
yellow,  sometimes  slightly  greenish  in  color,  becom- 
ing very  light  colored  when  heated  rapidly  to  its 
spontaneous  flashing  point.  On  further  heating  it 
takes  up  oxygen  very  rapidly,  becoming  thick  and 
darker,  until  finally  it  becomes  gummy. 

Probable  Adulterants.  Rosin  oil,  rosin,  mineral 
oils,  very  rarely  corn,  cottonseed,  and  menhaden 
oils.  As  regards  the  latter  named  oils  their  pres- 


86  THE  CHEMISTRY  OF  PAINTS 

ence  in  linseed  will  only  occur  when  the  difference 
in  cost  is  considerable.  It  should  be  borne  in  mind 
that  when  the  cost  of  linseed  is  as  much  as  five  cents 
a  gallon  advanced  over  the  cost  of  these  oils,  adul- 
teration with  them  offers  but  little  advantage  to  the 
crusher,  as  they  will  then  cost  him  about  as  much 
as  linseed.  A  shortage  of  seed  with  oil  contracts 
to  fill  might  lead  to  its  being  done  in  rare  instances. 

The  presence  of  rosin  oil  and  mineral  oil  will  be 
shown  by  the  flash  test.  The  sulphuric  test  may 
give  a  clue  to  the  one  present,  and  the  saponification 
number  the  amount.  Rosin  should  be  tested  for 
by  method  6.  The  iodine  number  may  very  often 
be  used  to  advantage,  but  it  should  be  remembered 
that  "foots"  in  the  oil  are  very  liable  to  lower  the 
iodine  absorption,  and  an  oil  to  be  tested  should 
be  clarified  if  possible.  "Foots"  can  hardly  be 
considered  adulteration,  but  offers  grounds  for 
complaint  against  an  oil,  causing  a  lowering  of  the 
saponification  as  well  as  of  the  iodine  number  and 
interfering  somewhat  with  drying.  Impure  seed 
often  imparts  a  foreign  taste  to  the  oil. 

Boiled  Oil.  —  Constants:  Sp.  gr.  15°  C.,  .^6-.^S. 
Iodine,  165-175.  Saponification,  190. 

This  oil  is  usually  prepared  by  heating  raw  oil 
to  about  250°  F.  and  adding  the  drier  (which  has 
been  previously  prepared  by  heating  raw  oil  to  a 
temperature  of  450°  to  500°  F.,  with  a  mixture  of 
lead  and  manganese  compounds  until  the  materials 
are  dissolved),  then  keeping  the  oil  at  that  tempera- 


PAINT  VEHICLES  87 

ture  for  several  hours.  So-called  "btmge  "  boiled  oils 
are  made  by  adding  the  drier  direct  to  the  raw  oil 
without  heat,  and  where  the  drier  is  made  from 
pure  linseed  are  practically  impossible  to  detect. 
As  is  often  the  case,  however,  the  drier  added  will 
contain  naphtha,  mineral  oil,  or  rosin  oil,  which  will 
at  once  be  shown  by  the  flash  test,  and  such  an  oil 
must  be  pronounced  adulterated. 

A  properly  boiled  oil  should  dry  in  eight  to  twelve 
hours,  but  the  fact  that  it  does  not  cannot  be  taken 
as  showing  adulteration,  but  may  be  due  to  the 
addition  of  too  little  drier. 

Boiled  oil  can  be  tested  for  purity  in  the  same 
manner  as  raw  linseed,  but  not  with  the  same  cer- 
tainty of  results.  The  dark  color  renders  the  sul- 
phuric test  of  little  value  excepting  when  consider- 
able adulteration  is  present,  and  also  obscures  the 
Halphen  reaction  if  cottonseed  is  present  in  small 
quantities.  The  presence  of  rosin  may  be  detected 
by  the  Lieberman-Storch  reaction.  Rosinates  used 
in  boiled  oil  as  a  drier  should  not  be  present  in 
quantities  sufficient  to  give  this  reaction.  The 
author  is  accustomed  to  test  boiled  oil  in  which 
rosin  is  found  by  mixing  to  a  paste  with  litharge 
and  allowing  to  stand  twenty-four  to  forty-eight 
hours.  Rosin  present  in  the  drier  as  rosinate  should 
not  be  in  sufficient  quantities  to  cause  the  mixture 
to  become  thick  or  perhaps  hard.  When  such  is  the 
case  the  oil  must  at  once  be  condemned.  It  will 
always  be  found  safer  not  to  use  a  boiled  oil  which 


88  THE  CHEMISTRY  OF  PAINTS 

gives  any  test  for  rosin.  Rosin  and  mineral  oils  will 
be  shown  by  the  flash  test,  and  the  amount  can  be 
approximated  by  determining  the  iodine  or  saponi- 
fication  number. 

Bleached  Oil.  —  Constants:  Sp.  gr.  at  15°  C.,  930- 
938.  Iodine  number,  170-180.  Saponification,  192. 

This  oil  may  be  prepared  by  treatment  of  raw 
oil  with  sulphuric  acid  and  steam;  a  mixture  of 
sulphuric  acid,  chromic  acid,  and  steam;  by  heating 
to  a  high  temperature  and  subsequently  chilling; 
by  heating  to  no°C.  and  forcing  air  and  steam 
through  it;  and  by  several  other  methods  involving 
similar  operations.  The  acid  bleached  is  generally 
used  for  paint  manufacturing,  while  the  fire  bleached 
is  sometimes  used  in  varnish  making  as  it  discolors 
less  when  heated  than  the  raw  or  acid  bleached  oils. 

The  constants  for  bleached  oils  vary  with  the 
method  employed  in  bleaching,  the  air  blown  hav- 
ing its  specific  gravity  increased  and  iodine  number 
diminished  over  value  given  above,  owing  to  the 
absorption  of  oxygen.  The  acid  bleached  should 
always  be  tested  for  sulphuric  acid  by  boiling  with 
water,  separating  and  testing  for  sulphates  with 
barium  chloride.  The  presence  of  acid  and  mois- 
ture will  be  found  to  affect  the  oil  when  it  is  mixed 
with  pigments,  increasing  the  amount  necessary 
to  grind  to  a  paste.  Test  for  purity  in  same  manner 
as  raw  oil.  A  varnish  maker's  bleached  oil  should 
have  an  iodine  number  of  180  and  bleach  white  at 

325°  c. 


PAINT  VEHICLES  89 

Lithographer's  Oil.  —  This  is  a  very  thick  linseed 
oil  prepared  by  long  boiling  at  a  high  temperature 
nearly  approaching  the  spontaneous  flashing  point; 
or  at  a  lower  temperature  by  forcing  air  through  it. 
It  is  used  chiefly  in  the  manufacture  of  printing  inks, 
but  occasionally  in  paints,  being  added  to  fillers, 
japans,  or  varnish  goods.  The  specific  gravity 
and  iodine  number  vary  with  the  thickness  of  the 
oil  and  are  of  little  value  in  determining  purity. 
Rosin,  rosin  oil,  and  light  mineral  oil  can  be  readily 
detected  by  the  usual  tests.  Mineral  oil  of  high 
flashing  point  could  be  detected  only  by  deter- 
mining the  saponification  number.  As  lithographer's 
oil  has  a  decided  bloom,  this  must  not  be  taken  as 
showing  the  presence  of  mineral  oil. 

China  Wood  Oil.  —  China  wood  oil  is  obtained 
by  cold  pressure  from  the  seeds  of  the  tung  tree,  a 
plant  which  grows  very  extensively  on  the  banks 
of  the  Yangtze  River  in  China.  It  has  recently 
come  into  extensive  use  in  the  manufacture  of 
varnish.  Its  peculiar  property  of  drying  flat,  with 
a  surface  somewhat  resembling  ground  glass,  has 
up  to  the  present  time  prevented  its  use  to  any 
extent  in  the  manufacture  of  paints.  Either  alone 
or  with  pigments  it  dries  with  a  dead  surface,  and 
even  when  used  in  a  small  proportion  with  other 
oils  and  varnish  it  tends  to  cause  flatting  and  some- 
times crinkling.  The  former  property  has  been 
utilized  to  produce  flatting  varnishes  without 
necessitating  the  use  of  wax. 


go          THE  CHEMISTRY  OF  PAINTS 

In  addition  to  the  above  property  China  wood 
oil  has  other  peculiarities  which  render  it  vastly 
different  from  all  other  drying  oils.  The  odor  is 
very  characteristic  and  stubbornly  resists  destruc- 
tion, regardless  of  the  manner  in  which  the  oil  is 
treated.  This  admits  of  its  identification  when 
present  in  but  small  proportions  in  varnishes,  etc., 
regardless  of  other  constituents.  Another  very 
interesting  property  is  the  instant  change  into  a 
jelly-like  substance  when  heated  to  about  285°  C. 
to  300°  C.  The  material  this  produces  is  insoluble 
in  all  ordinary  solvents  and  cannot  be  melted  by 
further  heating. 

The  properties  of  this  oil  that  have  led  to  its 
extensive  use  in  the  manufacture  of  varnish  are 
several.  The  oil  may  be  heated  without  discolora- 
tion; it  can  be  treated  so  as  to  remove  the  tendency 
to  flat,  and  then  produces  varnishes  with  a  very 
fine  gloss;  it  has  the  property  of  drying  hard  but 
tough,  and  when  used  with  rosin  will  produce  a 
more  elastic  varnish  than  will  linseed  oil.  Its  use 
has  made  possible  the  large  number  of  good  wear- 
ing varnishes  now  produced  at  a  low  cost. 

In  the  manufacture  of  light  driers  and  japans, 
this  oil  has  been  used  to  great  advantage.  Very 
powerful  light  driers  can  be  produced  by  dissolving 
in  it,  at  about  200°  C.,  red  lead  and  manganese 
rosinate  with  a  small  proportion  of  manganese 
borate  added.  The  latter  does  not  dissolve  to  any 


PAINT  VEHICLES  91 

appreciable  extent,  but  has  a  tendency  to  keep  the 
oil  lighter  in  color. 

The  best  grade  of  china  wood  oil  is  thicker  than 
linseed  oil,  and  very  light  in  color,  with  the  specific 
gravity  of  .944  at  15°  C.,  and  flashing  point  280°  C. 
It  dries  much  faster  than  linseed  and  in  a  somewhat 
different  manner.  The  drying  appears  to  take 
place  throughout  the  entire  body  of  the  oil  at  the 
same  time,  instead  of  from  the  top  down.  When 
heated  to  about  260°  C.  with  pure  manganese 
borate  the  oil  is  in  no  way  discolored  if  pure,  and 
even  has  a  tendency  to  become  lighter. 

A  most  peculiar  property  of  this  oil  is  exhibited 
by  this  treatment.  If  100  parts  of  the  oil  are  heated 
to  about  270°  C.  with  8  parts  white  manganese 
borate  until  a  scum  begins  to  form  on  top,  and  then 
mixed  with  as  much  as  700  parts  of  benzine  and 
allowed  to  stand  so  as  to  be  slightly  accessible  to 
air  for  a  few  days,  the  mixture  will  be  found  to 
consist  of  a  thick  water-white  liquid,  having  much 
the  appearance  of  gelatine.  If  allowed  to  remain 
longer  it  will  be  converted  into  a  white  translucent 
solid.  Before  the  latter  action  has  taken  place,  it 
may  be  mixed  with  oil  or  varnish,  which  if  added 
in  quantities  as  great  or  greater  than  equal  parts 
will  tend  to  stop  further  action.  The  same  action 
takes  place  if  less  borate  is  used,  but  more  slowly. 
This  is  also  the  case  when  turpentine  is  substituted 
in  place  of  benzine.  The  liquid  thus  produced 
differs  also  from  the  benzine  liquid  in  being  more 


92  THE  CHEMISTRY  OF  PAINTS 

like  varnish  in  appearance  than  like  gelatine,  i.e., 
not  being  so  "short." 

It  seems  more  than  probable  that  in  the  future 
this  oil  will  be  used  extensively  in  the  manufacture 
of  paints.  At  present  no  method  is  available  to 
remove  the  property  of  flatting  without  the  use  of 
more  heat  than  is  generally  at  the  command  of  the 
paint-maker. 

Menhaden  Oil.  —  Sp.  gr.,  ^'j-.g^.  Iodine  num- 
ber, 156-160.  Saponification  number,  190-192. 

This  oil  is  prepared  from  the  menhaden  fish  by 
steaming  and  subjecting  to  pressure.  It  varies 
from  the  very  dark,  strong  smelling  crude  to  the 
very  white  winter  bleached.  Caustic  soda  is  used 
in  refining.  By  proper  manipulation  all  grades 
can  be  completely  deodorized. 

Menhaden  oil  oxidizes  readily  in  the  air,  drying 
much  faster  than  linseed  but  never  gets  very  hard. 
It  wears  very  well  and  on  the  whole  is  the  most 
satisfactory  substitute  for  linseed  that  is  produced. 
Its  odor  has  prevented  its  use  in  paints,  but  it  seems 
probable  that  this  objection  will  be  overcome,  and 
when  this  is  accomplished  it  should  entirely  dis- 
place corn  and  cottonseed  oil  for  use  in  prepared 
paints. 

Probable  adulterants.  Rosin,  rosin  oil,  mineral 
oil.  Test  as  in  raw  oil. 

(B)  SEMI-DRYING  OILS 
Corn  Oil.  —  Constants:  Sp.  gr.,  .^20-^24.    Iodine 


PAINT  VEHICLES  93 

number,  115.  Flashing  Point,  245°  C.-2490  C.  Sa- 
ponification  number,  192. 

Corn  oil  is  prepared  from  the  germ  of  the  corn 
separated  during  the  manufacture  of  starch.  It  is 
light  in  color  and  has  a  very  characteristic  taste  and 
odor  resembling  corn.  Taste  and  odor  become 
noticeable  even  when  mixed  in  small  quantities 
with  linseed  oil. 

By  the  addition  of  a  large  amount  of  drier  corn 
oil  may  be  made  to  dry  after  prolonged  exposure  to 
the  air.  When  used  with  50  per  cent  or  more  of 
linseed  oil  and  the  necessary  amount  of  drier  it 
dries  fairly  well,  but  the  mixture  does  not  seem 
to  wear  as  well  as  pure  linseed  when  exposed  to 
the  action  of  the  weather. 

Probable  adulterants.  Rosin,  rosin  oil,  mineral 
oil.  Test  as  in  raw  oil. 

Cottonseed  Oil.  —  Constants:  Sp.  gr.,  .922-.9235. 
Iodine  number,  106-110.  Saponification  number, 

193- 

Cottonseed  oil  is  obtained  by  subjecting  the 
cottonseed  to  hydraulic  pressure.  The  crude  pressed 
oil  is  dark  red  in  color,  often  with  a  disagreeable 
odor.  It  is  purified  by  alkali,  yielding  a  light, 
pleasant  tasting  oil.  On  chilling,  large  quantities 
of  stearine  settle  out,  leaving  the  winter  white  oil. 

Cottonseed  oil  does  not  dry  as  well  as  corn  oil, 
but  otherwise  behaves  very  much  like  it  in  paint. 
When  a  large  amount  is  present  the  paint  will 
freeze  in  very  cold  weather,  owing  to  the  fact  that 


94  THE  CHEMISTRY  OF  PAINTS 

crude  cotton  and  oummer  yellow  begin  to  solidify 
at  about  o°  C. 

Probable  adulterants.  Rosin,  rosin  oil  and  mineral 
oil.  Test  as  in  raw  oil. 

(C)  NON-DRYING  OILS 

Rosin  Oil,  Mineral  Oil  (not  true  oils).  —  These 
materials  cannot  properly  be  classed  as  paint 
vehicles,  and  have  no  standing  in  a  reputable  paint 
factory.  They  can  be  used  to  some  advantage  in 
shingle  stains  when  the  object  is  to  leave  a  greasy 
surface  to  shed  rain,  also  in  small  quantities  in 
cheap  putty.  On  the  whole,  cheap  as  they  are, 
they  are  not  worth  their  cost  in  paints. 

Rosin  oil  may  be  found  adulterated  with  mineral 
oil,  but  mineral  oil  will  never  be  found  adulterated. 

II.  VARNISHES,  JAPANS,  AND  DRIERS 

Knowledge  of  their  physical  characteristics  and 
not  the  composition  of  these  materials  is  what  is 
desired  by  the  paint  chemist.  Samples  are  gen- 
erally submitted  to  be  substituted  for  those  in  use 
or  for  some  special  work.  In  the  former  case  they 
should  be  tested  against  the  stock  goods;  in  the 
latter,  with  the  object  in  view  for  which  they  are 
to  be  used. 

(a)  Driers,  Prepared.  —  A  properly  prepared  drier 
is  made  by  dissolving  manganese  and  lead  com- 
pounds in  hot  linseed  or  some  other  vegetable  oil 
and  thinning  with  turpentine  or  benzine.  A  drier 


PAINT  VEHICLES  95 

containing  much  free  rosin  or  rosin  oil  should  not 
be  used,  as  it  may  result  disastrously  when  used 
with  sublimed  products  or  red  lead,  and  under 
all  conditions  will  injure  the  life  of  the  paint.  The 
presence  of  rosinates  or  rosin  in  quantities  so  small 
as  to  withstand  the  litharge  test  can  be  used  with 
safety. 

LITHARGE  TEST.  —  Mix  the  drier  to  a  semi- 
paste  with  litharge  and  observe  the  length  of  time 
before  hardening.  The  best  driers  will  remain  for 
three  to  four  days  without  showing  any  thickening. 

Note.  As  different  brands  of  litharge  and 
those  containing  different  amounts  of  moisture, 
will  cause  a  great  variation  in  time  of  thickening 
with  driers,  etc.,  tests  should  always  be  made  with 
the  same  material  which  has  been  previously  well 
dried.  This  applies  to  varnishes  and  Japans  as 
well.  (See  Oil,  Paint  and  Drug  Reporter,  issue 
Sept.  22,  1902.) 

Test  drying  power  on  raw  oil,  using  various 
proportions  of  drier. 

Color  and  body  (when  latter  is  not  due  to  rosin, 
rosin  oil,  or  heavy  mineral  oil)  are  important  feat- 
ures. 

The  amount  of  benzine  may  be  determined  in 
supposed  turpentine  driers  by  method  given  under 
turpentine.  Other  conditions  being  the  same,  the 
drier  which  stands  the  longest  with  litharge  with- 
out hardening,  has  the  strongest  drying  power, 
lightest  color  and  heaviest  body,  has  the  best  value. 


96  THE  CHEMISTRY  OF  PAINTS 

As  thinners  should  also  be  taken  into  consideration 
it  will  be  found  very  difficult  to  pick  the  best  drier 
from  a  number  of  samples  without  considerable 
experience. 

Note.  The  manner  in  which  the  drier  dries  the 
oil,  and  not  the  drying  of  the  drier  itself,  as  so  many 
appear  to  think,  is  the  important  feature  in  this 
respect.  The  manner  in  which  the  drier  dries  alone 
will  not  give  the  slightest  indication  of  how  it  will 
dry  oil. 

(b)  Varnishes.  —  Varnishes  should  always  be 
tested  with  a  view  to  their  use.  The  important 
features  in  a  varnish  are  body,  color,  drying,  gloss, 
working  and  wearing  properties.  Where  a  varnish 
is  to  be  used  for  outside  work  it  should  always  be 
tested  by  exposure  to  the  weather,  best  on  well- 
oiled  hardwood.  Its  condition  should  be  noted  at 
frequent  intervals,  especially  after  rains. 

The  varnish  should  be  flowed  out  on  glass  and 
its  drying  noted,  also  hardness  and  toughness  after 
drying  several  days.  Color  is  very  important  where 
the  varnish  is  to  be  used  with  light  shades.  The 
gloss  should  be  tested  by  mixing  with  the  proper 
proportions  of  pigment  and  brushing  out,  at  the 
same  time  noting  how  it  flows  and  whether  or  not 
it  gives  a  smooth  surface. 

Body  is  also  of  importance,  and  where  the  varnish 
is  to  be  used  with  red  oxide  of  lead  vermilions  it 
should  always  be  tested  for  time  of  thickening  with 
litharge,  that  varnish  being  the  safest  to  use  which 


PAINT  VEHICLES  97 

stands  the  longest  with  litharge  without  thickening. 
It  is  always  advisable  to  have  a  large  number  of 
varnish  samples  at  hand,  all  of  whose  properties 
are  known,  so  that  when  one  having  certain  charac- 
teristics is  desired  it  may  be  obtained  without  delay. 

(c)  Japan,  Grinding.  —  In  testing  grinding  japan 
the  use  to  which  it  is  to  be  put  should  always  be 
kept  in  view.  Its  body,  color,  drying,  manner  in 
which  it  grinds,  and  amount  required  to  grind  any 
material  to  a  paste,  are  all  important  features. 
When  ground  with  pigment  and  rubbed  out  on  glass 
it  should  dry  flat  on  top,  but  should  not  appear 
flat  when  viewed  through  the  glass,  as  this  indicates 
deficiency  in  body.  It  should  dry  hard  in  eight  to 
ten  hours,  should  not  contain  naphtha,  and  the 
presence  of  rosin  in  any  quantities  should  be  avoided. 

When  a  japan  is  to  be  used  for  grinding  red 
oxide  of  lead  vermilions  great  care  must  be  taken 
in  its  selection.  A  japan  should  not  be  used  that 
will  harden  with  litharge  in  less  than  forty-eight 
hours,  and  even  this  can  only  be  safely  used  with 
the  highest  grade  of  orange  mineral  vermilions  if 
they  are  to  be  kept  in  stock  for  any  length  of  time. 
Vermilions  in  japan  and  varnish  should  only  be 
made  up  as  needed. 

The  author  very  strongly  advises  that  when 
satisfactory  grinding  japans  and  varnishes  are 
being  used,  great  caution  be  observed  in  changing, 
doing  so  only  after  practical  experiments  extend- 
ing over  a  considerable  space  of  time. 


98          THE  CHEMISTRY  OF  PAINTS 

(d)  Gloss  Oil.  —  This  material  is  made  by  melt- 
ing rosin  with  a  small  amount  of  lime  and  thinning 
with  benzine  or  sometimes  turpentine.  It  dries 
very  quickly  with  a  hard  brittle  surface  and  high 
gloss.  On  exposure  to  the  atmosphere  it  is  soon 
destroyed  and  can  never  be  used  alone  with  satis- 
factory results.  In  making  very  cheap  paints 
where  quick  drying  is  of  more  importance  than 
wearing  properties,  such  as  barrel  paint,  it  may  be 
used.  When  used  with  linseed  oil  it  gives  fair 
results  when  not  present  in  large  quantities,  but 
its  use  should  always  be  restricted  to  second-grade 
paints  and  used  very  cautiously  even  there.  It 
will  be  found  to  greatly  retard  drying  when  mixed 
with  linseed. 

III.    THINNERS 

Under  this  head  may  be  classed  turpentine, 
benzine,  rosin  spirits,  and  benzole,  the  first  two 
being  the  principal  materials  used,  and  the  last 
two  being  found  chiefly  in  turpentine  substitutes. 
Turpentine  manufactured  by  the  direct  distillation 
of  pine  waste  is  also  being  placed  on  the  market. 
This  varies  somewhat  in  composition  from  pure 
spirits  of  turpentine  and  cannot  be  rightly  sold  as 
such. 

Thinners  in  oil  paints  are  detrimental  to  the  life 
of  the  paint  if  not  properly  used,  and  should  best  be 
avoided.  Owing  to  the  fact  that  their  presence 
renders  the  application  of  paint  much  easier,  mak- 


PAINT  VEHICLES  99 

ing  it  less  laborious  to  brush  out,  their  use  has  be- 
come wide-spread  and  abused.  The  tendency  has 
been  to  reduce  the  amount  of  oil  below  that  required 
to  give  the  paint  its  proper  life,  and  to  greatly  in- 
crease the  amount  of  thinners,  especially  with 
benzine,  owing  to  its  cost.  This  will  be  found  to 
be  one  of  the  chief  causes  for  the  many  unsatis- 
factory mixed  paints  now  on  the  market. 

I.  Turpentine.  — Constants:  Sp.  gr.  15.5°  C.,  .862- 
.870.  Boiling  point,  156° C.-i58°C.  Flashing  point, 
36°  C.  (Abie's  Instrument). 

Turpentine  is  manufactured  by  distilling  pine 
resin  in  copper  stills.  The  temperature  must  be 
carefully  regulated  in  order  to  obtain  the  best  grade 
of  rosin  which  remains  behind  in  the  still.  The 
resin  from  the  first  season's  tapping  produces  the 
finest  quality  of  rosin,  i.e.,  water  white  and  window 
glass,  the  remaining  grades  varying  from  M  to  the 
black  A. 

Pure  turpentine  has  the  constants  as  given  above, 
is  colorless,  and  when  spread  out  over  a  large 
surface  evaporates  without  leaving  any  noticeable 
residue. 

Turpentine  offers  several  distinct  advantages 
over  benzine  as  a  thinner  in  paints  and  varnishes. 
First,  while  evaporating  at  ordinary  temperature 
it  will  not  flash,  which  greatly  reduces  the  danger 
from  fire;  second,  it  is  a  better  solvent  for  some 
gums;  third,  it  is  much  better  in  vehicles  used  for 
grinding  as  it  evaporates  much  slower  and  has 


100         THE  CHEMISTRY  OF  PAINTS 

less  tendency  to  make  pastes  "short";  and,  lastly, 
has  a  tendency  to  make  all  paints  which  contain  it 
flow  out  more  evenly  than  does  benzine.  It  has 
the  distinct  disadvantage  of  costing  many  times 
more,  however,  and  of  having  a  greater  tendency  to 
"flat"  where  this  may  not  be  desired.  This  is 
increased  by  the  fact  that  more  of  it  than  of  ben- 
zine is  required  to  reduce  a  paint  to  the  desired 
consistency,  owing  to  its  greater  body.  Its  so- 
called  drying  properties  lie  in  the  fact  that  when 
added  to  a  paint  less  oil  is  used,  the  body  is  dimin- 
ished, the  paint  spreads  over  a  greater  area,  natu- 
rally reducing  the  thickness  of  the  coat,  resulting 
in  faster  drying.  In  this  case  it  offers  no  advan- 
tage over  benzine,  which  will  produce  these  same 
results. 

THE  QUANTITATIVE  ESTIMATION  OF  ADULTERA- 
TION IN  TURPENTINE 

Sulphuric  Acid  Number. — The  following  method 
by  the  author,  while  not  giving  absolute  results  in 
all  cases,  will  be  found  to  be  very  accurate  for  the 
vast  majority.  This  test  should  be  first  employed, 
leaving  all  qualitative  tests  until  later,  as  this  alone 
may  establish  the  purity  of  the  sample  and  save 
unnecessary  work. 

Apparatus  and  materials:  Sample  turpentine 
of  known  purity,  66°  B.  sulphuric  acid,  neutral  oil, 
50  c.c.,  burette,  50  c.c.  and  10  c.c.  pipettes,  6-ounce 
beaker  packed  in  asbestos  fibre,  plaster  paris  mold, 


PAINT  VEHICLES  101 

or  any  suitable  material  for  retaining  heat,  ther- 
mometer o°-ioo°  C.,  finely  calibrated. 

The  operation,  which  should  always  be  made  with 
the  same  materials  and  apparatus,  is  proceeded 
with  as  follows :  — 

50  c.c.  neutral  oil  are  accurately  measured  in 
the  pipette  and  transferred  to  beaker,  temperature 
noted,  and  20  c.c.  66°  B.  sulphuric  acid  (which 
should  be  of  same  temperature  as  oil)  added 
slowly  from  the  burette,  the  time  being  of  no 
great  importance  so  long  as  it  be  slow  enough  to 
allow  the  acid  to  run  down  without  remaining  on 
the  sides  of  the  burette.  Now  stir  rapidly  to 
maximum  constant  temperature.  The  rise  will 
vary  from  o°  to  10°  C.,  depending  upon  the  grade 
of  neutral  oil  used.  This  rise  is  noted  and  kept 
for  future  reference.  It  is  advisable  not  to  use  a 
neutral  oil  giving  a  rise  of  over  2°  C. 

50  c.c.  neutral  oil  are  now  measured  as  before, 
10  c.c.  pure  turpentine  added,  the  temperature 
noted,  20  c.c.  sulphuric  added,  and  the  maximum 
rise  in  temperature  observed  after  stirring  thoroughly. 
(The  accuracy  of  the  results  depends  largely  on  stir- 
ring correctly.)  This  will,  of  course,  vary  with  the 
apparatus  used,  the  strength  of  the  acid,  and  the 
specific  heat  of  the  mineral  oil.  On  this  account  it 
is  impossible  to  calculate  the  "specific  temperature 
reaction"  as  in  the  Maumene"  test,  but  each  operator 
must  determine  his  own  factor  with  the  materials  used. 

The  rise  in  temperature  due  to  the  neutral  oil  is 


102        THE  CHEMISTRY  OF  PAINTS 


now  subtracted  from  that  due  to  the  turpentine 
present.  It  will  now  be  found  that  if  10  c.c.  ben- 
zine be  substituted  for  the  10  c.c.  turpentine,  the 
rise  in  temperature  will  be  the  same  as  with  the 
neutral  oil  (or  a  trifle  less,  owing  to  the  fact  that 
more  liquid  is  present).  The  increase  in  tempera- 
ture then  due  to  the  benzine  is  o°,  and  from  these 
observations  it  will  be  seen  how  the  percentage  of 
turpentine  in  a  mixture  of  turpentine  and  benzine 
can  be  readily  calculated,  the  benzine  being  ob- 
tained by  difference. 

The  author  gives  below  some  of  the  results  ob- 
tained by  himself:  — 

No.  I. 

50  c.c.  neutral  oil 

Sp.  gr.  .845 

20  c.c.  H2SO4  66° 

50  c.c.  neutral  oil 
10  c.c.  pure  "turps" 
20  c.c.  H2SO4 


Rise  in  temperature,  2°  C. 

No.  II. 

fi.  Rise  in  temperature  54°  C. 
1 2.  Rise  in  temperature  53}°C. 

5.  Rise  in  temperature  54  J°  C. 


Average  54° 

No.  III. 

50  c.c.  neutral  oil 
10  c.c.  benzine 
20  c.c.  H2SO4 

Therefore,  in  any  mixture  of  turpentine  and  ben- 
zine the  rise  in  temperature — 2°  C.X  1.923  gives  the 


Rise  in  temperature  =  2°  C. 


PAINT  VEHICLES 


percentage    turpentine    present    with    the   author's 
materials  and  apparatus. 


No.  IV. 
50  c.c.  neutral  oil 

25%  "turps" 


10  c.c. 


Rise=  i4f°  C. 


IO  C.C. 


Rise  =  28°  C. 


75%  benzine 
20  c.c.  H2SO4 
/.  %  turpentine  present  =(14!°— 2°=i2j°)X  1.923 

=  24.55%- 

No.  V. 

50  c.c.  neutral  oil 

50%  "turps" 

50%  benzine 
20  c.c.  H2SO4 
.'.  %  turpentine  =(28°— 2°)  X  i.  923  =  5°%- 

On  the  whole  it  has  been  the  author's  experience 
that  with  proper  care  the  percentage  turpentine  can 
be  readily  obtained  within  one  per  cent  of  the  cor- 
rect value.  A  trial  on  old  turpentine  and  distilled 
turpentine  which  have  not  been  subjected  to  the 
action  of  air  gives  results  the  same  as  on  the  fresh 
material. 

No.  VI. 

8  c.c.  turps        1    14  c.c.  distilled  off,  a  small  amount 
7.1  c.c.  benzine)       -of  turpentine  remaining  behind. 

The  distillate  was  shaken  to  assure  uniformity 
and  10  c.c.  taken. 


104         THE  CHEMISTRY  OF  PAINTS 
10  c.c.  distillate 


50  c.c.  neutral  oil 


Rise  in  temperature  =  2 yj0  C. 


20  c.c.  H2SO4 

/.  turpentine  present  =(2 7. 2 5 — 2°)  X  1.923  =  48.55 
%=%turpentine  in  10  c.c.  =  4.85  c.c.  turpentine  in 
10  c.c.,  or  10  c.c.  contains  5.15  c.c.  benzine. 

/.  5.15X1.4=7.2  c.c.  benzine  in  15.1  c.c.  sample. 
No.  VII. 

Sample  T  damar  varnish  containing  25  gallons 
benzine  per  100  gallons  varnish. 
30  c.c.  taken  and  15  c.c.  distillate  collected. 
10  c.c.  distillate 


50  c.c.  neutral  oil 


Rise  in  temperature  =2 9°  C. 


20  c.c.  H2SO4 

(29°— 2°)X  1.923  =  5!-9%  turpentine. 

=  5.19  c.c.  turpentine  in  10  c.c. 

dist. 

=  4.81  c.c.  benzine  in  10  c.c.  dist. 
=  7.2  c.c.  benzine  in  15  c.c.  dist., 
which  may  be  assumed  to  con- 
tain all  the  benzine  in  30  c.c. 
varnish. 

/.  as  determined,  100  c.c.  varnish  contains  24  c.c. 
benzine. 

It  will  be  seen  that  the  above  method  may  be 
employed  to  obtain  the  amount  of  benzine  in 
varnishes,  driers,  etc.,  which  are  sold  as  pure  tur- 
pentine products.  It  will  be  found  impossible  to 
distil  off  all  of  the  thinners,  but  if  turpentine  is 


PAINT  VEHICLES  105 

present  in  any  considerable  quantity,  and  the 
process  carried  to  such  a  point  that  no  further  dis- 
tillate will  come  over,  it  may  be  safely  assumed 
that  all  the  benzine  in  the  sample  is  present  in  the 
distillate,  and  the  amount  determined  as  above. 

Kerosene  gives  results  similar  to  benzine,  and 
when  shown  qualitatively  by  remaining  behind  on 
paper  after  evaporation  of  turpentine  should  be 
determined  in  the  same  manner. 

The  presence  of  benzole  and  rosin  spirits,  which 
may  sometimes  be  found  in  turpentine  and  turpen- 
tine substitutes,  would  complicate  matters  consider- 
ably. As  regards  benzole  a  sample  examined  by 
the  author  gave  results  similar  to  benzine  and 
readily  determined,  but  a  mixture  of  benzole,  ben- 
zine, and  turpentine  could  only  be  approximated. 
In  such  a  case  the  turpentine  could  be  accurately 
obtained,  but  the  benzole  and  benzine  could  only  be 
approximated  by  calculation  from  the  specific 
gravity,  assuming  the  specific  gravity  of  benzole 
to  be  the  same  as  turpentine. 

Rosin  spirits  will  be  found  to  still  further  com- 
plicate matters,  as  it  gives  a  small  rise  in  tempera- 
ture with  sulphuric  acid.  The  following  result 
was  obtained  on  a  sample  of  rosin  spirits  of  known 
purity,  specific  gravity  .871:  — 


10  c.c.  rosin  spmts 
50  c.c.  neutral  oil 
20  c.c.  H2SO4 


Rise  in  temperature 
10°  C.,  rise  due  to 
rosin  spirits,  8°  C. 


io6        THE  CHEMISTRY  OF  PAINTS 

Whether  or  not  the  rise  in  temperature  of  rosin 
spirits  is  a  constant  the  author  finds  it  impossible 
to  state,  owing  to  the  difficulty  found  in  obtaining 
samples.  Assuming  that  it  is,  and  qualitative 
tests  show  its  presence,  no  great  error  would  be 
made  in  calculating  the  amount  of  turpentine  as  in 
benzine,  if  the  rosin  spirits  be  present  in  small 
quantities.  When  present  in  any  considerable 
quantities,  the  amount  of  turpentine  can  be  esti- 
mated as  in  presence  of  benzine,  the  amount  of 
rosin  spirits  obtained  by  difference  and  the  per 
cent  of  turpentine  recalculated,  taking  into  account 
the  rise  due  to  the  rosin  spirits.  If  benzine  also  is 
present,  quantitative  estimations  of  all  three  would 
be  impossible,  but  by  determining  the  percentage 
of  turpentine  as  if  nothing  but  benzine  were  present, 
then  calculating  the  percentage  of  benzine  present 
by  specific  gravity  (assuming  the  specific  gravity 
of  rosin  spirits  to  be  the  same  as  turpentine),  finally 
recalculating  the  turpentine,  taking  into  considera- 
tion the  rise  in  temperature  due  to  the  rosin  spirits 
as  determined,  results  may  be  obtained  that,  while 
they  cannot  be  depended  upon  to  any  extent  (unless 
the  turpentine  is  present  in  very  much  greater 
amounts  than  is  the  rosin  spirits)  may  often  be 
found  of  value.  The  amount  of  rosin  spirits  pro- 
duced is  so  small,  however,  that  it  is  doubtful  that 
it  is  in  any  way  used  to  adulterate  turpentine.' 

In  testing  the  purity  of  turpentine,  then,  the  above 
test  should  be  first  applied.  If  the  proper  result 


PAINT  VEHICLES 


107 


is  obtained  no  further  test  is  necessary  to  establish 
the  purity  of  the  sample.  If  such  is  not  the  case 
adulteration  is  certain.  As  the  method  gives  the 
percentage  turpentine  direct,  the  percentage  adultera- 
tion is  known  except  when  complications  may  arise 
by  the  presence  of  wood  turpentine  and  other  ma- 
terials mentioned  above.  Wood  turpentine  itself 
gives  results  similar  to  adulterated  turpentine. 
Adulteration,  however,  can  be  established  by  the 
following  table  and  the  two  articles  thus  distin- 
guished from  each  other: 


Sulphuric 
Acid 
Number. 

Specific 
Gravity. 

Flashing 
Point. 

Boiling 
Point. 

Evaporation 
on  Paper. 

Adulterating 
Material 
Present. 

Low. 

Low. 

Low. 

Low. 

No  Residue. 

Benzine. 

Low. 

O.K. 

Low. 

Low. 

No  Residue. 

Benzole. 

Low. 

Low. 

O.K. 

O.K. 

Greasy 
Stain. 

Kerosene. 

Low. 

O.K. 
or  High. 

Low. 

Low. 

Greasy 
Stain. 

Unrefined 
Rosin 
Spirits. 

Low. 

O.K. 

O.K. 

O.K. 

Little  or  no 
Residue. 

Refined 
Rosin 
Spirits, 
or  Wood 
Turpentine. 

O.K. 

O.K. 

O.K. 

O.K. 

No  Residue. 

None. 

A    closed    tester    should  be    used    to   determine 
the  flashing  point.     Any  appreciable  quantities  of 


io8        THE  CHEMISTRY  OF  PAINTS 

benzine  or  benzole  will  cause  the  sample  to  flash 
at  ordinary  temperature,  i.e.,  about  23°  C. 

The  specific  gravity  should  be  determined  with 
either  the  Westphal  balance  or  the  specific  gravity 
bottle  in  conjunction  with  a  delicate  analytical 
balance. 

By  boiling  point  is  meant  that  temperature  at 
which  boiling  first  begins.  Turpentine,  consisting 
as  it  does  of  a  mixture  of  several  terpenes  of  different 
boiling  points,  has  not  one  definite  temperature  at 
which  it  is  completely  distilled,  as  is  the  case  with  a 
single  chemical  compound  such  as  water. 

Wood  turpentine  in  any  quantity  will  be  shown 
only  by  the  sulphuric  acid  number  and  by  any  pecu- 
liarity of  odor  it  may  possess.  (See  also  Wood  Tur- 
pentine.) 

The  nature  of  the  adulterating  material  having 
now  been  established  by  the  above,  tests  as  well  as 
by  the  odor,  the  calculation  of  the  composition  of 
the  sample  is  taken  up  as  given  under  the  sul- 
phuric acid  number. 

Wood  Turpentine.  —  This  article,  which  is  manu- 
factured by  the  direct  distillation  of  pine  waste,  is 
beginning  to  occupy  an  important  position  as  a 
substitute  for  turpentine.  Samples  from  different 
manufacturers  examined  by  the  author  show  a  con- 
siderable difference  chemically  from  spirits  of  tur- 
pentine and  from  each  other,  although  all  have 
practically  the  same  percentage  composition. 

These  samples  all  appeared  quite  as  satisfactory 


PAINT  VEHICLES  109 

to  use  as  spirits  of  turpentine,  as  well  as  having  the 
same  specific  gravity,  nearly  the  same  boiling  point, 
evaporating  in  the  same  time,  and  not  flashing  at 
ordinary  temperature.  With  one  exception  all  were 
quite  different  in  odor. 

This  difference  in  odor  alone  cannot  be  urged  as 
an  objection  to  the  sale  of  this  article  under  the 
brand  of  spirits  of  turpentine.  The  peculiar  odor 
of  turpentine  is  due  to  aldehyde-like  products 
caused  by  the  action  of  light  and  air.  The 
presence  of  creosote  in  wood  turpentine  would  of 
course  be  an  impurity,  but  this  should  be  elimi- 
nated by  thorough  washing  with  caustic  soda 
before  the  final  distillation,  to  dissolve  the  phenol 
and  cresols  present.  As  is  known,  the  odor  of 
ordinary  turpentine  varies  with  age  and  action  of 
sunlight,  and  a  difference  in  odor  between  turpentine 
prepared  by  two  different  methods  can  no  more 
be  urged  as  showing  the  impurity  of  one  than  can 
the  difference  in  odor  between  acid-bleached  and 
fire-bleached  linseed  oil  be  propounded  as  showing 
one  of  these  products  to  be  impure. 

Aside  from  the  odor,  however,  a  distinct  chemical 
difference  is  found  when  the  wood  turpentine  is 
treated  by  the  sulphuric  acid  method.  The  follow- 
ing table  shows  the  per  cent  rise  in  temperature 
compared  to  spirits  of  turpentine,  of  four  samples 
tested  by  the  author  when  subjected  to  this  test 
as  well  as  other  results  obtained  on  the  same  ma- 
terials. 


no        THE  CHEMISTRY  OF  PAINTS 


SPECIFIC 
GRAVITY. 

BOILING 
POINT. 

PER  CENT  RISE 

WITH  H2SO4 

COMPARED  TO 
TURPENTINE. 

Sample  No.  i  —  .862 

159°  C. 

7544 

Sample  No.  2  —  .863 

156°  C. 

74 

Sample  No.  3  —  .863 

158°  C. 

65.6 

Sample  No.  4  —  .864 

156°  C. 

97.6 

1.  Odor  resembled  pine  needles. 

2.  Odor  same  as  No.  i,  but  stronger. 

3.  Odor  stronger  than  No.  2,  with  penetrating 
odor  similar  to  formaldehyde  and  leaving  a  residual 
odor  of  cresote  on  evaporation. 

4.  Odor  in  bulk  practically  the  same  as  spirits  of 
turpentine,  but  that  left  after  evaporation  slightly 
stronger. 

Of  the  above,  these  results  show  Nos.  i,  2,  and  3 
different  to  a  considerable  degree  from  turpentine. 
The  action  is  a  negative  rather  than  a  positive  one, 
and  because  No.  4  gives  nearly  the  same  rise  in 
temperature  as  does  turpentine,  it  cannot  be  stated 
absolutely  that  it  is  nearly  the  same  chemically, 
although  such  is  very  probably  the  case.  The 
chemistry  of  the  terpenes  is  not  very  well  understood 
at  present,  and  all  the  reactions  that  take  place  on 
the  addition  of  concentrated  sulphuric  acid  cannot 
be  stated  with  certainty. 


PAINT  VEHICLES  in 

American  turpentine  consists  largely  of  pinene 
(C10H16),  which  is  converted  into  camphene  (C10H16) 
by  concentrated  sulphuric  acid,  and  this  in  turn  is 
converted  into  polymeric  modifications  of  the 
formulae  C15H24>  and  C^H^  (colophene).  The 
reaction  is  undoubtedly  much  more  complicated 
when  this  method  is  used  than  above  stated,  the 
large  amount  of  sulphuric  causing  decompo- 
sition. 

Dipentene,  a  constituent  of  Russian  and  Swedish 
turpentine,  is  produced  by  heating  terpenes  to  a 
high  temperature  and  is  a  product  in  the  distillation 
of  pine  roots.  It  is  formed  in  American  turpentine 
by  heating  to  250°  C.-27o°  C.,  as  well  as  by  the 
action  of  dilute  sulphuric  acid.  Sylvertrene  is  also 
formed  by  the  distillation  of  pine  roots. 

To  return  to  wood  turpentine,  assuming  that  it 
differs  in  some  respects  from  spirits  of  turpentine, 
the  question  arises  of  what  this  difference  consists. 
It  is  obviously  impossible  for  the  commercial  chemist 
to  take  up  this  subject  in  the  laboratory  and  it  must 
be  left  to  the  research  laboratory  to  be  discovered, 
while  even  here  it  may  be  impossible  to  determine 
until  the  chemistry  of  the  terpenes  is  more  thoroughly 
understood  than  at  present.  In  the  meantime  con- 
jectures as  to  the  probable  difference  between  these 
articles  may  be  indulged  in,  and  the  author  offers 
the  following  to  explain  the  difference  in  composi- 
tion between  them :  — 

First,  there  is  the  possible  presence  of  creosote, 


112         THE  CHEMISTRY  OF  PAINTS 

ketones,  acetone,  etc.,  if  the  product  is  not  care- 
fully prepared,  but  these  are  not  liable  to  occur  in 
an  article  carefully  manufactured,  except  in  traces. 
The  most  acceptable  explanation  is  that  wood  tur- 
pentine contains  less  pinene  than  spirits  of  turpen- 
tine, and  a  greater  amount  of  terpenes  of  isomeric 
and  polymeric  composition.  In  support  of  this 
can  be  offered  the  formation,  as  given  above,  of 
dipentene  by  heating  turpentine  to  250°  C.  Now, 
of  the  four  samples  examined,  No.  4  was  produced 
at  a  low  temperature  by  the  latest  machinery. 
Nos.  i,  2,  and  3  were  produced  at  a  higher  tempera- 
ture, although  how  high  the  author  is  unable  to  say. 
Again,  if  the  heat  generated  by  the  addition  of 
concentrated  sulphuric  acid  is  caused  by  the  trans- 
formation of  pinene  into  polymeric  modifications, 
it  would  follow  that  if  this  transformation  had 
already  taken  place  to  some  extent  the  heat  developed 
on  the  addition  of  the  acid  would  be  decreased, 
which  is  found  to  be  the  case. 

Parties  manufacturing  samples  Nos.  i,  2,  and  3 
offer  them  for  sale  as  a  pure  turpentine,  differing 
only  from  American  turpentine  in  odor,  due  to 
the  process  by  which  they  are  made.  As  re- 
gards sample  No.  4  it  would  seem  that  with  a  little 
more  care  this  product  could  be  made  identical 
with  American  turpentine,  in  which  case  parties 
manufacturing  it  have  a  perfect  right  to  sell  it  as 
such. 

As  regards  its  use  in  adulterating  turpentine,  it 


PAINT  VEHICLES  113 

would  seem  that  the  probability  of  this  is  at  present 
overestimated.  The  majority  of  these  products 
could  not  be  used  with  turpentine  in  sufficient 
quantities  to  pay  without  their  presence  being 
detected.  If  one  can  be  produced  pure  enough  to 
sell  without  question  as  American  turpentine  it 
should  command  the  same  price. 

Benzole,  Ninety  per  Cent.  —  Benzole  is  a  bi- 
product  in  the  destructive  distillation  of  coal. 
Ninety  per  cent  benzole  is  so-called  because  90 
per  cent  is  distilled  before  the  temperature  rises 
above  100°  C.  The  average  percentage  of  constitu- 
ents of  a  good  quality  is  about  70  per  cent  benzene, 
24  per  cent  toluene,  including  a  little  xylene,  and 
from  4  to  6  per  cent  of  light  hydrocarbons  and 
carbon  disulphide. 

The  compound  benzene  (C6H6),  the  lowest 
member  of  the  benzene  series  of  hydrocarbons, 
should  not  be  confused  with  benzine  derived  from 
petroleum,  from  which  it  is  entirely  different.  Treated 
with  a  cooled  mixture  of  concentrated  H2SO4  and 
HNO3  at  a  temperature  below  50°  C.,  it  is  converted 
into  nitro-benzene  or  oil  of  myrbane.  On  treat- 
ment with  nascent  hydrogen,  generated  by  the 
action  of  HC1  on  iron  filings,  this  is  converted  into 
aniline  which  enters  largely  into  the  manufacture 
of  many  artificial  dyes. 

Benzole  is  a  clear,  water- white  liquid,  flashing 
at  ordinary  temperature  and  having  a  peculiar 
characteristic  odor.  It  is  an  excellent  solvent  for 


THE  CHEMISTRY  OF  PAINTS 

many  gums,   oils,   and  waxes.     It  finds  its  chief 
use  in  the  paint  trade  as  a  constituent  of  paint  and 
varnish  remover. 
Benzine,  63°.     (See  Turpentine.) 


APPENDIX 
PIGMENTS  RARELY  ENCOUNTERED 

Lithophone.  —  A  combination  of  zinc  sulphide 
(with  small  amounts  of  oxide)  and  sulphate  of 
barium,  made  by  adding  solutions  of  ZnSO4  and 
BaS,  of  such  strength  as  to  completely  precipitate 
one  another.  The  grade  usually  found  on  the 
market  and  considered  standard  contains  about 
65  per  cent  BaSO4,  the  remainder  being  ZnS  with 
small  amounts  of  ZnO. 

Lithophone  is  very  white  and  has  good  body, 
but  is  not  popular  owing  to  the  fact  that  it  cannot 
be  used  in  conjunction  with  lead  in  any  form  with- 
out the  possible  formation  of  the  black  PbS.  As 
lead  exists  in  some  form  or  another  in  practically 
all  varnishes,  driers,  and  japans  the  use  of  litho- 
phone  is  very  limited.  Its  presence  can  always 
be  detected  (in  the  absence  of  ultramarine)  by  the 
evolution  of  H2S  gas  on  the  addition  of  acid. 

The  determination  of  bases  present  as  well  as 
SO3  may  be  made  in  the  same  manner  as  in  the  analy- 
sis of  white  paints.  Determine  sulphur  by  oxidizing 
with  fuming  nitric  acid  in  a  closed  flask.  Add 
some  NaCl  and  HC1  and  evaporate  the  excess  of 
nitric  acid.  Dilute,  filter,  heat,  and  precipitate 
with  a  hot  solution  of  BaCl2.  After  subtracting  any 
sulphates  previously  obtained,  calculate  remainder 

us 


n6        THE  CHEMISTRY  OF  PAINTS 

to  ZnS,  all  remaining  zinc  being  expressed  as 
ZnO. 

Paris  Green  [3CuOAs2O3Cu(O2H3O2)2].— A  com- 
bination of  copper  and  arsenic  having  a  very  bright 
shade  but  deficient  in  body  and  tinting  power. 
On  this  account,  combined  with  the  fact  that  it  is 
extremely  poisonous,  its  use  is  at  present  practically 
limited  to  that  of  a  germicide.  Its  purity  may  be 
tested  by  NH4OH,  in  which  it  is  completely  soluble 
to  a  blue  solution. 

Zinc  Chromate  (ZnCrO4). — A  very  light  yellow 
with  a  decided  greenish  cast.  It  has  not  the 
value  of  lead  chromate  and  is  more  difficult  and  ex- 
pensive to  make.  The  solution  must  be  neutral  in 
reaction  after  precipitation,  to  make  it  complete. 
Its  analysis  may  be  made  in  the  same  manner  as 
lead  chromate. 

Barium  Carbonate  (BaCO3)  is  being  used  by  at 
least  one  manufacturer  in  the  production  of  paste 
and  liquid  paints.  Its  presence  might  be  mistaken 
for  whiting  if  the  flame  test  were  not  applied  on 
original  sample,  or  it  might  be  precipitated  with 
H2SO4  and  be  mistaken  for  lead.  Its  occurrence  in 
samples  is  so  rare  that  most  chemists  may  never 
encounter  it.  If  sulphate  of  lead  or  calcium  are 
present  certain  amounts  of  BaCO3  will  be  precipi- 
tated as  BaSO4,  and  this  will  not  carry  through 
with  calcium.  In  the  samples  encountered  by  the 
author  it  was  used  in  conjunction  with  zinc  oxide 
alone.  The  small  amount  of  BaSO4  left  insoluble 


APPENDIX  117 

was  considered  as  precipitated  by  the  sulphate  in 
the  zinc  calculated  to  BaCO3  and  added  to  the  re- 
mainder found. 

To  determine  BaCO3,  precipitate  with  ammonia 
and  ammonium  carbonate,  after  all  lead  and 
third-group  metals  have  been  precipitated  by 
NH4OH  and  H2S.  Any  calcium  present  will  be  pre- 
cipitated in  conjunction  with  it.  Filter  on  Gooch 
crucible,  dry,  heat  gently,  adding  small  quantities 
of  ammonium  carbonate  to  convert  any  CaO  formed 
to  CaCO3.  Weigh  combined  carbonates,  dissolve 
in  HC1,  filter  out  asbestos  and  precipitate  barium 
with  very  dilute  H2SO4  hot.  Decant,  boil  with 
water  to  which  a  small  quantity  of  HC1  is  added 
to  dissolve  any  CaSO4  precipitated,  decant  and  re- 
peat, finally  washing  BaSO4  on  filter  with  boiling 
water  until  free  from  acid.  Dry,  ignite,  and  weigh 
as  BaSO4  and  calculate  to  BaCO3,  obtaining  calcium 
as  CaCO3  by  subtracting  from  total  previously 
found. 


n8         THE  CHEMISTRY  OF  PAINTS 


TABLE   I. 

ATOMIC   WEIGHTS 
OF  THE    PRINCIPAL   ELEMENTS. 


NAME 

SYMBOL 

ATOMIC 
WEIGHT 

NAME 

SYMBOL 

ATOMIC 
WEIGHT 

Aluminium  . 

Al 

27   I 

Lithium 

Li 

702 

Antimony  .  .    . 

Sb 

I2O.  2 

Magnesium 

Mg 

•  wo 

24    36 

Arsenic  

As 

7<C.  o 

Manganese 

Mn 

er    o 

Barium  

Ba 

137-4 

Mercury  . 

Hg 

OD  »w 

2OO    O 

Bismuth  

Bi 

208.1: 

Molybdenum 

Mo 

06  o 

Boron  

B 

II.  O 

Nickel  .  . 

Ni 

58    7 

Bromine 

Br 

70  06 

Nitrogen    .... 

N 

14   O4 

Cadmium 

Cd 

112    4 

Oxygen      .  . 

o 

16  o 

Calcium 

Ca 

4O    I 

Phosphorus  .  . 

P 

31    O 

Carbon 

c 

12    O 

Platinum  

Pt 

104   8 

Chlorine  

Cl 

•JIT  .4.C 

Potassium  

K 

•7Q     I  C 

Chromium  .... 

Cr 

52.  I 

Silicon  

Si 

28.40 

Cobalt  

Co 

">Q-  O 

Silver  

Ag 

108.0 

Copper  .  . 

Cu 

63.6 

Sodium  

Na 

23.01: 

Fluorine 

F 

IO    O 

Strontium 

Sr 

87  6 

Gold 

Au 

107    2 

Sulphur 

s 

32    06 

Hydrogen 

H 

Ay/  •  - 
i  008 

Tin 

Sn 

I  IQ    O 

Iodine 

I 

127    O 

Uranium 

u 

238    < 

Iron 

Fe 

CC      Q 

Zinc      

Zn 

2       •> 
CK    4 

Lead              .    . 

Pb 

Jj-y 
206.  o 

Zirconium  

Zr 

*>  7 
oo.  6 

APPENDIX 


119 


TABLE    II. 
MOLECULAR   WEIGHTS. 

Calculated  on  basis  of  O  =  16.     H=  i. 


NAME. 

CHEMICAL 
FORMULA. 

MOLECULAR 
WEIGHT. 

Alum  

K2Al2(SO4)4+  24H2O 

Od8  74. 

Aluminium  oxide  

A12O3 

IO2  2O 

hydroxide  .  .  . 
sulphate 

A12(OH)6 
A12(SO4)3 

156.20 

Ammonium  hydroxide.  .  . 
chloride  .... 
Barium  oxide  

NH4OH 
NH4C1 
BaO 

6*+*  '6° 

35-04 

53-49 

JC7   AQ 

'         carbonate  ...... 
'         chloride 

BaCOa 
BaCl2  +  2H2O 

197.40 

hydroxide  
'         sulphate  
Calcium  carbonate  
'         oxide  
'         sulphate 

Ba(OH)2 
BaSO4 
CaCOa 
CaO 
CaSO4 

171.40 
23346 

IOO.IO 

56.10 

Bichromate  of  soda 

Na2Cr2Oy 

"  potash... 
Chromate  of  soda  
"   potash  
Chromic  oxide  

K2Cr2O7 
Na2CrO4 
K2CrO4 
Cr2O3 

294.50 

162.20 

194.40 

I  52  20 

Ferric  chloride 

Fe2Clfl 

"      oxide 

Fe2Oa 

o^4ou 

"      sulphate    

Fe2(SO4)3 

•7QQ    Q§ 

Ferrous  sulphate  

FeSO4 

TCT   06 

Lead  carbonate  

PbCOa 

266  9O 

"      chloride  

PbCl2 

277  80 

chromate  

PbCrO4 

227  OO 

hydroxide  
White  lead  (basic  carbon- 
ate)   
Lead  oxide  (litharge).  .  .  . 
oxide  (red  lead)  .... 
"     sulphate  
Magnesium  carbonate  .  .  . 
oxide  
pyrophosphate 
Manganese  dioxide  
pyrophosphate 

Pb(OH)2 

2PbCO3Pb(OH)2 
PbO 
Pb304 
PbS04 
MgCOa 
MgO 
Mg2P2O7 
MnO2 
Mn2P2O7 

240.90 

774.70 
222.9O 
684.70 
302.96 
84.36 
40.36 
222.72 
87.00 
284.00 

120        THE  CHEMISTRY  OF  PAINTS 
TABLE  II. —  Continued. 


NAME. 

CHEMICAL 
FORMULA. 

MOLECULAR 
WEIGHT. 

Potassium  chlorate 

KC1O3 

cyanide 

KCN 

hydroxide  .... 
iodide  ...    . 

KOH 
KI 

v^.-iy 

56.15 

166  ic 

oxide  .... 

K2O 

permanganate  . 
platinic  chloride 
"          sulphate     
Silica  

KMnO4 
K2PtCl6 
K2S04 
SiO2 

isz-is 
485.80 

I74-36 

60  4. 

Sodium  bicarbonate  ..... 

NaHCO3 

84  o< 

"        carbonate  

Na2CO3 

106  10 

"        chloride  

NaCl 

C.8  CQ 

"        hydroxide  

NaOH 

4O.OC. 

"        oxide  

Na2O 

VJ.v$ 
O2.  IO 

<k       sulphate  

Na2SO4 

142.16 

"        thio-sulphate  .... 
Zinc  carbonate  

Na2S203+5H20 
ZnCO3 

248.22 
125.40 

chloride  

ZnQ2 

136.30 

oxide  

ZnO 

81.40 

"     sulphate  

ZnSO4 

161.46 

"     sulphide  

ZnS 

07.46 

ACIDS. 


NAME. 

CHEMICAL 
FORMULA. 

MOLECULAR 
WEIGHT. 

Acetic    

HC2H3O2 

60.00 

Carbonic  (anhydride)  
Hydrochloric 

C02 
HC1 

44.00 

^6  4? 

Hydrobromic 

HBr 

80  96 

Hydroiodic  

HI 

I28.OO 

Hydrosulphuric 

H2S 

34.o6 

Nitric  

HNO3 

63.04 

Oxalic  

H2C2O4+2HoO 

£ 
1  2O.OO 

Sulphuric 

H2SO4 

08.06 

(anhydride).... 
Sulphurous    . 

S03 
H2SO3 

80.06 
82.06 

APPENDIX 


121 


TABLE    III. 

FACTORS. 


ONE 
PER  CENT 

OF 

Is  EC 

JUTVALENT 
TO 

ONE 
PER  CENT 

OF 

Is  EQUIVALENT 

TO 

A1203.... 

1.5285  c 

Y0  A12(OH)6 

Cr2O3  .... 

1.3153  %Cr03 

A1203  .... 

3-3492 

A12(S04)3 

PbCrO4  .  . 

.4060  "  Na2Cr2O7 

AlzOs.... 

9.2831 

Alum 

PbCrO4  .  . 

.4557  "  K2Cr2O7 

BaSO4  .  .  . 

.8922 

BaCl2 

Fe2O3  .... 

.7000  "  Fe 

BaS04... 

-8455 

BaC03 

Fe2O3  .... 

.9000  "  FeO 

BaS04... 

.6618 

BaO 

PbS04... 

.6830  "  Pb 

BaS04... 

.6089 

Na2S04 

PbS04... 

.833    "  Am.  Ver. 

BaS04  .  .  . 

1.2976 

PbS04 

PbS04... 

.8809  "  PbCO3 

BaS04... 

•5831 

CaSO4 

PbS04... 

.8523  "  White  lead 

BaS04  .  .  . 

•!373 

S 

PbS04... 

.7357  "  PbO 

BaS04... 

-343° 

S03 

PbS04... 

1.0662  "  PbCrO4 

BaS04... 

.4201 

H2S04 

PbS04... 

.753     "  Pb3O4 

BaS04... 

.6916 

ZnS04 

PbS04... 

.4494  "  CaSO4 

CaO  

2.4271 

CaS04 

PbS04... 

.7705  "  BaS04 

CaO  

1.7840 

CaC03 

PbS04... 

.5329  "  ZnSO4 

CaCO3... 
CaSO4  .  .  . 

1.3602 
•7351 

CaSO4 
CaCOa 

Mg2P2O7  . 
Mg2P2O7  . 

•7575  "  MgC03 
.6396  "  P2O6 

CaS04... 

2.2250 

PbS04 

Na2O  .... 

1.7086  "  Na2CO8 

C02  

2.2750 

CaC03 

Na20.... 

1.2898  "  NaOH 

CO2  

8.8034 

White  lead 

NaOH  .  .  . 

1.4020  "  KOH 

Cr2O3  .... 

4.2444 

PbCrO4 

ZnO  

.8034  "  Zn 

Cr2O3  .... 

8.0200 

Am.  Ver. 

ZnSO4  .  .  . 

.5041  "  ZnO 

Cr2O3  .... 

1-9349 

K2Cr207 

ZnS04  .  .  . 

1.8763  "  PbSO4 

Cr203.... 

1.7234 

Na2Cr2O7 

122         THE  CHEMISTRY  OF  PAINTS 


TABLE  IV. 


OIL   CONSTANTS. 


NAME 
OF  OIL. 

Specific 
gravity 
at  15.5°  C. 

Flashing 
Point. 
Open  tester 
°C. 

Grams 
Iodine 
absorbed  by 
100  grams  oil. 
Iodine  number. 

Mgms.  KOH 
necessary  to 
saponify 
i  gram  oil. 
Saponifica- 
tion  number. 

Castor       .    .    . 

.963   -.968 
.9225—  .9236 
.9215-.  924 
•93  1  2  --9334 
•9336-  -936 
Variable 
.917 
.929  -.932 
.9145—  .9168 
.986 



83.6 
106.8—  no.i 

"5 
170    —187 
167    —170 
12.8-    26.1 
76.2 
156    —  160 
78.9-   86.4 
67.9 

I78 

193 
191 
191 
190 
No  action 
195 
190 
194 

Cottonseed  .... 
Corn  

245-49 
295 
275 

Linseed  * 
Linseed,  boiled 
Mineral 

Lard   

e    (  winter  \ 
252Wained) 

Menhaden  
Olive 

Rosin  

Variable 

APPENDIX 


123 


TABLE  V. 

TABLE   OF  EQUIVALENTS. 

Centigrade =F.—  32  x  f . 

Centigram  , . .  =     0.1543  grain. 

Centimeter =     0.3937  inch- 

Cubic  foot  of  water =  62.4  pounds. 

Cubic  foot  of  water =     7.48  gallons. 

Dram  (Apoth.  or  Troy). . .  =     3.9  grams. 

Fahrenheit =^^+32 

Foot =     0.3048  meter  or  30.48  centimeters. 

Gallon  (U.  S.) =     3.785  liters. 

Gallon  of  water  (U.  S.)  . . .  =  8|  pounds. 
Gallon  of  water  (Imperial)  =  10  pounds. 

Gram  (Troy) =     0.0648  gram. 

Gram =   15-432  grains. 

Inch  =     2 .54  centimeters. 

Meter =  39.3704  inches. 

Ounce  (Avoirdupois) =   28.35  grams. 

Ounce  (Troy  or  Apoth.). . .  =  31.104  grams. 
Pound  (Avoirdupois) =453.603  grams. 


TABLE  VI. 

PRINCIPAL  BASIC  AND  ACID   RADICALS   FOUND 
IN   PAINTS. 


H2O 
A1203 
BaO 
CaO 


Cr2O3 
Fe2O3 
PbO 
Pb304 


MgO 
Mn02 
HgO 
Na20 


ZnO 
SiO2 
S03 
C02 


CN 
Cr03 

S 


124        THE  CHEMISTRY  OF  PAINTS 


TABLE  VII. 

Specific  Gravity  of  Sulphuric  Acid  at  60°  F.  compared  to 
Water  at  60°  F. 

Standard  of  The  Manufacturing  Chemists'  Association  of  the  U.  S. 


Be\° 

Sp.  Gr. 

Per  cent 
H2SO4 

Be".0 

Sp.  Gr. 

Per  cent 
H<S04 

Be.0 

Sp.  Gr. 

Per  cent 
H2SO4 

66. 

1.8354 

93.19 

34- 

1.3063 

39-92 

J7- 

1.1328 

18.71 

65.75 

1.8297 

91.80 

33- 

1.2946 

38.58 

16. 

1.1240 

17.53 

65.5 

1.8239 

90.60 

32. 

1.2832 

37-26 

I5- 

1.1154 

16.38 

65.25 
65. 
64.75 
64-5 

1.8182 
1.8125 
.8068 
.8012 

89.55 
88.65 
87.81 
87.04 

3L 
30. 
29. 
28. 

1.2719 
1.2609 
1.2500 
L2393 

35-93 
34-63 

33.33 
32.05 

14. 
J3- 

12. 
II. 

1.1069 
1.0985 
1  .0902 
1.0821 

15.25 
14.13 
13.01 
11.89 

64-25 

-7957 

86-33 

27. 

1.2288 

3°-79 

10. 

1.0741 

10.77 

64. 

.7901 

85.66 

26. 

1.2185 

29-53 

9- 

1.0662 

9.66 

63- 

.7683 

83.34 

25- 

1.2083 

28.28 

8. 

1.0584 

8.55 

62. 

.7470 

81.30 

24. 

1.1983 

27.03 

7- 

1.0507 

7-45 

61. 

.7262 

79-43 

23. 

1.1885 

25.81 

6. 

1.0432 

6-37 

60. 

.7059 

77.67 

22. 

1.1789 

24.61 

5- 

I>°357 

5.28 

59- 

.6860 

75-99 

21. 

1.1694 

23-43 

4- 

1.0284 

4.21 

58. 

.6667 

74.36 

20. 

i.  1600 

22.25 

3- 

I.O2II 

3-I3 

57- 

.6477 

72.75 

19. 

1.1508 

21.07 

2. 

I.OI40 

2.08 

56. 

.6292 

71.17 

18. 

1.1417 

19.89 

I. 

1  .0069 

i.  02 

55- 

.6111 

69-65 

54- 

•5934 

68.13 

53- 

.576i 

66.63 

52. 

•5591 

65.13 

Si- 

.5426 

63.66 

ALLOWANCE  FOR  TEMPERATURE. 

50. 

•5263 

62.18 

49. 

.5104 

60.75 

At  10°  Be".  .029°  Be.  or  .00023  sp.  gr.  for       F. 

48. 

.4948 

59-32 

At  20°  "    .036°   "    "    .00034       "        "        F. 

47- 

•4796 

57-9° 

At  30°  "    .035°  "    "   .00039       "        "        F. 

46. 

.4646 

56.48 

At  40°  "    .031°   "    "    .00041       "        "        F. 

45- 

.4500 

55-07 

At  50°  "    .028°  "    "   .00045       "        "        F- 

44- 

•4356 

53-66 

At  60°  "    .026°  "    "    .00053       "        "        F. 

43- 

.4216 

52.26 

At  63°  "    .026°  "    "   .00057       "        "        F. 

42. 

.4079 

50.87 

At  66°  "    .0235°"     "   .00054       "        "        F. 

41. 

-3942 

4947 

40. 

.3810 

48.10 

39. 

•3679 

46.72 

38. 

.3551 

45-35 

37- 

.3426 

43-99 

36. 

•33°3 

42.63 

35. 

.3182 

41.27 

APPENDIX 


125 


TABLE  VIII. 

Specific  Gravity  of  Nitric  Acid  at  60°  F.  compared  to 
Water  at  60°  F. 

Standard  of  the  Manufacturing  Chemists'  Association  of  the  U.  S. 


Be\° 

Sp.  Gr. 

Per  cent 
HN03 

Be\° 

Sp.  Gr. 

Per  cent 
HNO3 

Be\° 

Sp.  Gr. 

Per  cent 
HNO3 

10. 

.0741 

12.86 

40. 

1.3810 

61.38 

44-5 

1.4428 

75-40 

ii. 

.0821 

14.13 

40.5 

1.3876 

62.77 

45- 

1.4500 

77.17 

12. 
13. 

.0902 
.0985 

15-41 
16.72 

41. 
4L5 

1.3942 
1.4010 

64.20 
65.67 

45-5 
46. 

'•4573 
1.4646 

79.03 
8  1.  08 

14. 

.1069 

18.04 

42. 

1.4078 

67.18 

46.5 

1.4721 

83.33 

15- 

•1154 

19.36 

42.5 

1.4146 

68.73 

47- 

1.4796 

85.70 

16. 

.1240 

20.69 

43- 

1.4216 

7°-33 

47-5 

1.4872 

88.32 

17. 

.1328 

22.04 

43-5 

1.4286 

71.98 

48. 

1.4948 

91.35 

18. 

.1417 

23.42 

44- 

1.4356 

73.67 

48.5 

1.5026 

95-" 

19. 

.1508 

24.82 

20. 

.1600 

26.24 

21. 

.1694 

27.67 

22. 

.1789 

29.07 

23. 

.1885 

3°-49 

24. 

.1983 
.2083 

3L94 
33-42 

ALLOWANCE  FOR  TEMPERATURE. 

26! 

.2185 

34-94 

At  io°-2o°  Be".,  3^°  Be",  or  .00029  sp.  gr.  for  i°  F. 

11: 

29. 

.2288 

.2393 
.2500 

36.48 
38.06 
39-66 

At  2o°-3o°  Be".,  ^  Be",  or  .00044      "         "    x°  F. 
At  3o°-4o°  Be".,  ^V  Be"-  or  -0006       "         "    i°  F- 

30. 

.2609 

41.30 

At  400-48.s°  Be\,  Ty  Be\  or  .00084  "         "    i°  F 

31. 

.2719 

43-00 

32. 

.2832 

44.78 

33- 

.2946 

46.58 

34- 

-3063 

48.42 

35- 

.3182 

50-32 

36. 

•33°3 

52-30 

it 

.3426 
•3551 

54.36 

39- 

.3679 

58.82 

39-5 

•3744 

60.06 

I26         THE  CHEMISTRY  OF  PAINTS 


TABLE    IX. 

Specific  Gravity  of  Hydrochloric  Acid  Solutions  at  60°  F. 
compared  to  Water  at  60°  F. 

Standard  of  the  Manufacturing  Chemists'  Association  of  the  U.  S. 


Be\° 

Sp.  Gr. 

Per  cent 
HC1. 

I. 

1  .0069 

1.40 

2. 

1.0140 

2.82 

3- 

I.  O2  1  1 

4-25 

4- 

1.0284 

5.69 

5- 

I-°3S7 

7.IS 

6. 

1.0432 

8.64 

7- 

1.0507 

10.17 

8. 

1.0584 

11.71 

9- 

1.0662 

13.26 

10. 

1.0741 

14.83 

ii. 

1.0821 

16.41 

12. 

i  .0902 

18.01 

J3- 
14. 

.0985 
.1069 

19.63 
21.27 

ALLOWANCE  FOR  TEMPERATURE. 

IS- 

•1154 

22.92 

io°-is°  Be".,  ?y»  Be.  or  .0002  sp.  gr.  for  i°  F. 

16. 

16.5 

!?• 

.1240 
.1283 
.1328 

24-57 
25-39 
26.22 

iS°-22°  Be*.,  ¥y  Be",  or  .0003  sp.  gr.  for  i°  F. 
22°-2S°  Be\,  jV  Be",  or  .00035  sp.  gr.  for  i°  F. 

x7-5 

•!372 

27.07 

18. 

.1417 

27.92 

18.5 

.1462 

28.78 

19. 

.1508 

29.65 

iQ-5 

•1554 

30-53 

20. 

.1600 

31-45 

20.5 

.1647 

32.38 

21. 

.1694 

33-31 

21.5 

.1741 

34.26 

22. 

.1789 

35-2i 

22.5 

.1836 

36.16 

23- 

.1885 

37-14 

23-5 

•!934 

38.26 

24. 

.1983 

39-41 

24.5 

•2033 

40-55 

25- 

.2083 

41.72 

25-5 

•2134 

43-40 

APPENDIX 


127 


TABLE    X. 

Specific  Gravity  of  Acetic   Acid  at    15°  C.  compared  to 
Water  at  4°  C. 


SPECIFIC 
GRAVITY 
AT  15°  C. 

PER 
CENT 
C2H4O2 

SPECIFIC 
GRAVITY 

AT  15°  C. 

PER 
CENT 
C2H402 

SPECIFIC 
GRAVITY 
AT  15°  C. 

PER 
CENT 
C2H402 

1.0007 

i 

1.0470 

35 

1.0729 

69 

1.0022 

2 

1.0481 

36 

I-°733 

70 

1.0037 

3 

1.0492 

37 

1.0737 

7i 

I.OO52 

4 

I.O5O2 

38 

1.0740 

72 

1.0067 

5 

LOS^ 

39 

1.0742 

73 

1.0083 

6 

1-0523 

40 

1.0744 

74 

I.OOgS 

7 

L0533 

4i 

1.0746 

75 

I.OII3 

8 

1.0543 

42 

1.0747 

76 

I.OI27 

9 

1.0552 

43 

1.0748 

77 

I.OI42 

10 

1.0562 

44 

1.0748 

78 

I.OI57 

ii 

1.0571 

45 

1.0748 

79 

I.OI7I 

12 

1.0580 

46 

1.0748 

80 

1.0185 

13 

1.0589 

47 

1.0747 

81 

I  .O2OO 

14 

1.0598 

48 

1.0746 

82 

I.02I4 

IS 

1.0607 

49 

1.0744 

83 

I.O228 

16 

1.0615 

5° 

1.0742 

84 

1.0242 

17 

1.0623 

51 

1.0739 

85 

1.0256 

18 

1.0631 

52 

1.0736 

86 

I.O27O 

19 

1.0638 

53 

1.0731 

87 

1.0284 

20 

1.0646 

54 

1.0726 

88 

1.0298 

21 

1.0653 

55 

1.0720 

89 

I.03II 

22 

i  .0660 

56 

1.0713 

90 

1.0324 

23 

1.0666 

57 

1.0705 

9i 

1-0337 

24 

1.0673 

58 

1.0696 

92 

1.0350 

25 

1.0679 

59 

1.0686 

93 

1.0363 

26 

1.0685 

60 

1.0674 

94 

1-0375 

27 

1.0691 

61 

i.  0660 

95 

1.0388 

28 

1.0697 

62 

i  .0644 

96 

1  .04OO 

29 

1.0702 

63 

1.0625 

97 

I.O4I2 

30 

1.0707 

64 

1.0604 

98 

I.O424 

31 

1.0712 

65 

1.0580 

99 

1.0436 

32 

1.0717 

66 

1-0553 

IOO 

1.0447 

33 

1.0721 

67 

1.0459 

34 

1.0725 

68 

128         THE  CHEMISTRY  OF  PAINTS 


TABLE    XI. 

Specific  Gravity  of  Caustic  Soda  Solution  at  15°  C.  com- 
pared to  Water  at  4°  C. 

(LUNGE) 


SPECIFIC 
GRAVITY 
AT  15°  C. 

PER  CENT 
NaOH. 

SPECIFIC 
GRAVITY 
AT  15°  C. 

PER  CENT 
NaOH. 

1.007 

.61 

I.22O 

19.58 

1.014 

1.20 

1.231 

20.59 

I.  O2  2 

2.00 

I.24I 

21.42 

I.O29 

2.71 

1.252 

22.64 

1.036 

3-35 

1.263 

23.67 

1.045 

4.00 

1.274 

24.81 

1.052 

4-64 

1.285 

25.80 

1.  000 

5-29 

1.297 

26.83 

1.067 

5-87 

1.308 

27.80 

1-075 

6-55 

1.320 

28.83 

1.083 

7-31 

1.332 

29-93 

I.O9I 

8.00 

1-345 

31.22 

.IOO 

8.68 

1-357 

32.47 

.108 

9.42 

i-37° 

33-69 

.116 

10.06 

1-383 

34.96 

.125 

10.97 

1-397 

36-25 

•134 

11.84 

1.410 

37-47 

.142 

12.64 

1.424 

38.80 

.152 

13-55 

1.438 

39-99 

.162 

14.37 

1.453 

41.41 

.171 

1.468 

42.83 

.ISO 

15.91 

1.483 

44-38 

.190 

16.77 

1.498 

46.15 

.2OO 

17.67 

1.514 

47.60 

I.2IO 

18.58 

I-53° 

49.02 

APPENDIX 


129 


TABLE   XII. 


Specific  Gravity  of  Ammonia  Solutions  at  60°  F.  compared 
to  Water  at  60°  F. 

Standard  of  the  Manufacturing  Chemists'  Association  of  the  U.  S. 


Be\° 

Sp.  Gr. 

Per  cent 
NH3 

10. 

1  .0000 

.00 

ii. 

.9929 

1.62 

ALLOWANCE  FOR  TEMPERATURE. 

12. 
*3' 

•9859 
.9790 

3-3° 

5.02 

Correction 

to  be  subtracted 

from  each  degree 

14. 

.9722 

6.74 

Q     .._. 

above  60°  F. 

J5- 
16. 

i7- 

•9655 
•9589 
.9524 

0-49 
10.28 

12.  IO 

Degrees 
BaumS 

70°  F. 

80°  F. 

90°  F. 

ioo8F. 

18. 
19. 

20. 
21. 
22. 
23- 

•9459 
•9396 

•9333 
.9272 
.9211 
.9150 

13.96 
15.84 
17.76 
19.68 
2  1.  60 
23-52 

$ 

18° 

20° 
22° 
26° 

.020°  Be. 
.026° 
-031° 
.037° 
-043° 
•057° 

.022°  Be. 
.028°    " 
•033°    " 
•°38° 

•°45o 
•059 

.024°  Be. 
•030°    " 
.035°    ' 
.040° 
•047°    " 

.026°  Be\ 

•°*2i  ;; 

•037° 
.042°    " 

24. 

.9091 

25.48 

25- 

.9032 

27.44 

26. 

.8974 

29.40 

27. 

.8917 

3J-36 

28. 

.8861 

33-32 

29. 

.8805 

35-28 

130        THE  CHEMISTRY  OF  PAINTS 


TABLE    XIII. 

Specific   Gravity  of  Ethyl   Alcohol   and   Percentage   by 
Weight  at  150  C. 

(FOWNES) 


SPECIFIC 
GRAVITY 
AT  15°  C. 

PER 
CENT 
C2H60 

BY 

WEIGHT 

SPECIFIC 
GRAVITY 
AT  15°  C. 

PER 
CENT 
C2H60 

BY 

WEIGHT 

SPECIFIC 
GRAVITY 
AT  15°  C. 

PER 
CENT 
C2H60 

BY 

WEIGHT 

.9981 

i 

.9490 

35 

•8745 

69 

•9965 

2 

.9470 

36 

.8721 

70 

•9947 

3 

•9452 

37 

.8696 

7i 

•993° 

4 

•9434 

38 

.8672 

72 

.9914 

5 

.9416 

39 

.8649 

73 

.9898 

6 

•9396 

40 

.8625 

74 

.9884 

7 

•9376 

4i 

.8603 

75 

.9869 

8 

•9356 

42 

.8581 

76 

•9855 

9 

•9335 

43 

•8557 

77 

.9841 

10 

•93  H 

44 

•8535 

78 

.9828 

ii 

.9292 

45 

.8508 

79 

.9815 

12 

.9270 

46 

.8483 

80 

.9802 

13 

.9249 

47 

•8459 

81 

.9789 

14 

.9228 

48 

•8434 

82 

.9778 

15 

.9206 

49 

.8408 

83 

.9766 

16 

.9184 

5° 

.8382 

84 

•9753 

17 

.9160 

5i 

•8357 

85 

.9741 

18 

•9*35 

52 

•8331 

86 

.9728 

19 

•9  "3 

53 

•8305 

87 

.9716 

20 

.9090 

54 

.8279 

88 

.9704 

21 

.9069 

55 

.8254 

89 

.9691 

22 

.9047 

56 

.8228 

90 

.9678 

23 

.9025 

57 

.8199 

9i 

.9665 

24 

.9001 

58 

.8172 

92 

.9652 

25 

•8979 

59 

.8145 

93 

.9638 

26 

•8956 

60 

.8118 

94 

.9623 

27 

•8932 

61 

.8089 

95 

.9609 

28 

.8908 

62 

.8061 

96 

•9593 

29 

.8886 

63 

.8031 

97 

•9578 

3° 

.8863 

64 

.8001 

98 

.9560 

31 

.8840 

65 

.7969 

99 

•9544 

32 

.8816 

66 

•7938 

IOO 

.9528 

33 

•8793 

67 

•95" 

34 

.8769 

68 

INDEX 


Aluminium,   determination   as 

oxide,  i. 
in  ochre,  43. 
in  silicates,  13,  14. 
separation  from  iron,  i. 
American  vermilion,  30. 
Apparatus,  Bunsen's,  n. 

for    the   determination  of 

carbonates,  3. 
for  the   determination   of 
water,     "turps,"     and 
benzine  in  paints,  62, 65. 
Appendix,  115. 

Barium,  determination  as  sul- 
phate, i. 
separation   from   calcium 

2. 
Barium  carbonate,  116. 

analysis  of,  116. 
Barytes,  30. 

analysis  of,  31. 
separation  from  silica  and 

silicates,  12. 
Basic  lead  chromate,  30. 

separation  from  red  lead, 

Benzine,  98,  114. 

in  turpentine,  102. 
Benzole,  113. 

in  turpentine,  105. 
Black  pigments,  20. 

bone,  20. 

carbon,  20. 

ivory,  20. 

lamp,  21. 
Blue  pigments,  16. 

Chinese,  16. 

Prussian,  17. 

ultramarine,  17. 


Bone  black,  20. 

analysis  of,  20. 
Brown  pigments,  22. 

umber,  22. 

vandyke,  23. 

graphite,  24. 

Calcium,  determination  as  ox- 
ide, 2. 

separation  from  barium,  2. 
Carbon,  in  black,  20. 

in  graphite,  24. 

in  vandyke  brown,  23. 
Carbon  black,  20. 

analysis  of ,  20. 
Carbon  di -oxide,  determination 

of,  3- 
China  clay,  32. 

combined  water  of,  32. 

analysis  of,  12,  13,  32. 
Chinese  blue,  16. 

analysis  of,  50. 
China  wood  oil,  89. 
Chromium,    determination    as 
oxide,  4. 

insoluble  chromates,  n. 

separation  from  iron,  7. 

separation    from    manga- 
nese, 10. 

soluble  chromates,  4. 
Chrome  orange,  41. 

analysis  of,  u,  50. 
Chrome  yellow,  41. 

analysis  of,  n,  42,  50. 

in  tinted  paints,  66. 
Chrome  green,  25. 

analysis  of,  25,  50. 
Corn  oil,  92. 
Cottonseed  oil,  93. 

Halpen's  test  for,  84. 


132 


INDEX 


Driers,  prepared,  94. 
Dry  and  untinted  colors,  quali- 
tative analysis  of,  47. 
quantitative  analysis  of,  50. 

English  vermilion,  27. 

analysis  of,  27. 
Eosine  vermilion,  27. 

analysis  of,  54. 

Graphite,  24. 

analysis  of,  24. 
Green  pigments,  25. 

chrome,  25. 

Paris,  1 1 6. 
Gloss  oil,  98. 
Gypsum,  33. 

analysis  of,  33. 

in  paints,  58. 

Thompson's     method     of 
determining,  48. 

Iodine,  titration  of,  5. 
Iodine,     absorption     method, 
Hiibl,  77. 
Wijs,  78. 
Iron,   determination   as   ferric 

oxide,  6. 

determination  with  potas- 
sium permanganate,  7. 
separation    from    alumin- 
ium, i. 

separation   from   chro- 
mium, 7. 

separation    from    manga- 
nese, 10. 
Iron  oxide,  26. 

analysis  of,  26. 
in  ochre,  43. 
in  sienna,  44. 
Ivory  black,  20. 

Japan,  grinding,  97. 

Lamp  black,  21. 
Lead,    determination    as    sul- 
phate, 9. 
basic  carbonate,  39. 


basic  chromate,  30. 
chromate,  41. 
oxide,  42. 
sulphate,  34. 

Linseed  oil,  raw,  85. 

boiled,  86. 

bleached,  88. 

lithographers,  89. 
Lithophone,  115. 

analysis  of,  115. 

Magnesium,  determination  as 
pyrophosphate,  9. 

carbonate,  33. 

silicate,  33. 

Manganese,   determination   as 
oxide,  10. 

determination  of  di-oxide, 
ii. 

in  sienna,  44. 

in  tinted  paints,  66. 

in  umber,  22. 

separation  from  iron,  10. 
Mixed  paints,  61. 

analysis  of,  see  white  and 

tinted  paints. 
Matching  of,  dry  colors,  67. 

permanent  reds,  69. 

ultramarine  tints,  74. 

untinted   colors   in   paste, 
70. 

white   and   tinted   pastes, 
72. 

white   and   tinted   paints, 
72. 

yellow  ochre  tints,  74. 
Menhaden  oil,  92. 
Mineral  oil,  94. 

determination  of  in  vege- 
table oils,  79. 

in  driers,  95. 

Ochre,  yellow,  43. 

analysis  of,  12,  13,  43. 

in  tinted  paints,  59. 
Oil,    determination    in    mixed 
paint,  61. 


INDEX 


Oils,  China  wood,  89. 

corn,  92. 

cottonseed,  93. 

linseed,  85. 

menhaden,  92. 

mineral,  94. 

rosin,  94. 

Oils,    tests    on,  —  flash   test, 
81. 

Halpen's  test,  84. 

iodine  number,  Hiibl,  77. 

iodine  number,  Wijs,   78. 

rosin  test,  84. 

saponification  number,  79. 

sulphuric  acid  test,  82. 

taste  and  odor,  83. 
Orange  mineral,  see  red  lead. 
Orange   pigments,   see  yellow 
pigments. 

Paints,  see   white  and   tinted 

paints. 

Paris  green,  116. 
Permanent  red,  28. 

analysis  of,  52. 

tests  to  determine,  29. 
Plaster  Paris,  33. 
Prussian  blue,  17. 

analysis  of,  50. 

Qualitative  analysis  of  paints, 

47- 
Quantitative  analysis  of  paints, 

So- 
Rapid  method  for  analysis  of 
sublimed  products,  38. 
Rapid  method  for  analysis  of 
white  and  tinted  paints, 
58. 
Red  lead  and  orange  mineral, 

42. 

in  vermilion,  27. 
determination   of  in   ver- 
milion, 54. 
separation  from  basic  lead 

chromate,  55. 
Red  pigments,  26. 


Rosin,  test  for,  84. 
in  boiled  oil,  87. 
in  driers,  95. 

Saponification   number,    79. 
Sienna,  raw  and  burnt,  44. 

analysis  of,  45. 
Silica,  34. 

analysis  of,  12,  13. 

separation    from    barytes, 

12. 
Silicates,  analysis  of,  12,  13. 

separation    from    barytes, 

12. 

Strength  test,  15. 
Sublimed  lead,  34. 

analysis  of,  37. 

composition  of,  35. 
Sulphates,     determination     as 

barium  sulphate,  14. 
Sulphur,  in  lithophone,  115. 

in  ultramarine,  19. 

Tables,  atomic  weights,  118. 

color  tests,  29. 

equivalents,  123. 

factors,  121. 

molecular  weights,  119. 

paint  radicals,  123. 

oil  constants,  122. 

showing  impurities  in  tur- 
pentine, 107. 

specific  gravity  of  acetic 
acid,  127. 

specific  gravity  of  ammo- 
nia solutions,  129. 

specific  gravity  of  caustic 
soda  solutions,  128. 

specific  gravity  of  ethyl 
alcohol,  130. 

specific  gravity  of  hydro- 
chloric acid  solutions, 
126. 

specific  gravity  of  nitric 
acid,  125. 

specific    gravity    of    sul- 
phuric acid,  124. 
Thompson's  method,  48. 


134 


INDEX 


Tinted  paints,  see  white  and 

tinted  paints. 
Turpentine,  analysis  of,  100. 

benzine  in,   102. 

benzole  in,  105. 

determination  of  flashing 
point  of,  107. 

determination    of   specific 
gravity  of,  108. 

determination    of    boiling 
point  of,  1 08. 

kerosene  in,  105. 

rosin  spirits  in,  105. 

table  for  determining  im- 
purities in,  107. 

wood  turpentine  in,   107. 

Ultramarine,  17. 

analysis  of,  18. 

in  tinted  paints,  60. 
Umber,  raw  and  burnt,  22. 

analysis  of,  22. 

Vandyke  brown,  23. 

analysis  of,  23. 
Varnish,  96. 
Vermilion  pigments,  27. 

American,  30. 

English,  27. 

cosine,  27. 

permanent,  28. 

scarlet,  27. 

Water,  in  China  clay,  32. 

in  paints,  62,  65. 
White  pigments,  30. 

barytes,  30. 

China  clay,  32. 

gypsum,  33. 

magnesium  carbonate,  33. 

magnesium  silicate,  33. 

silica,  34. 

sublimed  lead,  34. 

white  lead,  39. 

whiting,  38. 

zinc,  American,  36. 

zinc,  French,  40. 


zinc  lead,  35. 
Whiting,  38. 

analysis  of,  39. 
White  lead,  39. 

analysis  of,  40. 

White      and      tinted      paints, 

chrome  yellow  tints,  66. 

determination  of  pigment 

in,  61. 

determination    of    water, 
"turps,"     and    benzine 
in,  62,  65. 
ochre  tints,  59. 
qualitative  analysis  of,  47. 
quantitative    analysis    of, 

55-°°- 
rapid  method  for  analysis 

of,  58. 

treatment  of  sample,   46. 
ultramarine  tints,  60. 
Wood  turpentine,  108. 

difference   from  spirits  of 

turpentine,  no. 

Yellow  ochre,  43. 

analysis  of,  12,  13,  43. 

in  tinted  paints,  59. 
Yellow  and  orange  pigments, 
41. 

chrome  yellow,  41. 

chrome  orange,  41. 

red  lead  and  orange  min- 
eral, 42. 

sienna,  44. 

yellow  ochre,  43. 

zinc  chromate,  116. 

Zinc,  determination  as  oxide, 

14. 
Zinc  chromate,  116. 

analysis  of,  116. 
Zinc  lead,  35. 

analysis  of,  37. 
Zinc  oxide,  American,  36. 

analysis  of,  37. 
Zinc  oxide,  French,  40. 

analysis  of,  41. 


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plates  and  72  illustrations.  8vo,  cloth net,  $2.50. 

JAMESON,  LEWIS.    The  Manufacturers'  Practical  up-to-date 

Recipe  Book.  Nearly  3,000  practical  up-to-date  recipes 
for  manufacturing  all  kinds  and  qualities  of  colors,  paints, 
varnishes,  japans,  enamels,  oils,  greases,  lubricants,  soaps, 
etc.,  and  for  all  manufactures  connected  with  the  allied 
trades.  Buyers'  and  sellers'  simple  and  reliable  tests  for 
materials,  adulterations,  etc.  8vo,  cloth.  4  volumes, 

each net,  $15.00 

Vols.  I.,  II.,  III.,  pertaining  to  Paints,  Oils,  etc.,  as  follows: 
Contents:  Vol.  I.  569  pp.  Pigments  and  Dry  Colours, 
Paste  and  Mixed  Paints,  Paint  Oils,  Vehicles,  and  Medi- 
ums, Distempers,  and  Sundry  Paint  Materials.  —  Vol.  II. 
412  pp.  Varnishes  and  Varnish  Derivatives,  Oils  and 
Other  Varnish  Materials,  Oil  and  Spirit  Varnishes, 
Printing  and  Litho  Inks,  Enamels,  Anti-Foulings,  Gold 


STANDARD  WORKS  — Continued 

Paints,  etc.  — Vol.  III.  477  pp.  Oils,  Fats,  Tallows, 
Waxes  and  Greases  (Vegetable,  Animal,  and  Mineral), 
for  Burning,  Lubricating,  Leather  Dressing,  etc.,  and  for 
all  purposes. 

JENNINGS,   A.   S.    Paint   and   Color  Mixing:   A   Practical 

Hand-book  for  Painters,  Decorators,  and  all  who  have  to 
mix  colors.  Containing  seventy-two  samples  of  paint  of 
various  colors,  including  the  principal  graining  grounds 
and  upwards  of  four  hundred  different  color  mixtures, 
with  hints  on  color  and  paint  mixing  generally,  testing 
colors,  recipes  for  special  paints,  etc.  8vo,  cloth,  illus- 
trated, 97  pp net,  $2.00. 

JENNISON,  FRANCIS  H.  The  Manufacture  of  Lake  Pig- 
ments from  Artificial  Colours:  A  useful  handbook  for 
colour  manufacturers,  dyers,  colour  chemists,  paint  manu- 
facturers, drysalters,  wall-paper  makers,  enamel  and 
surface-paper  makers.  With  fifteen  plates  illustrating  the 
various  methods  and  errors  that  arise  in  the  different  pro- 
cesses of  production.  8vo,  cloth,  illustrated.  .  .  .net,  $3.00. 

JONES,  M.  W.    The  Testing  and  Valuation  of  Raw  Materials 

Used  in  Paint  and  Color  Manufacture.  i2mo,  cloth 
net,  $2 .00. 

LAMBERT,   THOMAS.    Lead    and    its    Compounds.    With 

tables,  diagrams  and  folding  plates.  8vo,  cloth,  illus- 
trated, 228  pp net,  $3.50. 

LIVACHE,  ACH.  The  Manufacture  of  Varnishes,  Oil  Crush- 
ing, Refining  and  Boiling  and  Kindred  Industries.  De- 
scribing the  Manufacture  and  Chemical  and  Physical 
Properties  of  Spirit  Varnishes;  and  Oil  Varnishes;  Raw 
Materials;  Resins;  Solvents  and  Coloring  Principles; 
Drying  Oils,  Their  Extraction,  Properties,  and  Applica- 
tions; Oil  Refining  and  Boiling;  the  Manufacture,  Em- 
ployment and  Testing  of  Various  Varnishes.  Translated 
from  the  French  by  John  Geddes  Mclntosh.  Greatly 
extended  and  adapted  to  English  practice,  with  numerous 
original  recipes,  by  the  translator.  8vo,  cloth,  illustrated. 

Vol.  I  net,  $3.50. 

(To  be  complete  in  three  volumes.) 

MUCKLEY,   W.   J.    A   Hand-book   for   Painters   and   Art 

Students  on  the  Character,  Nature,  and  Use  of  Colors. 
Fourth  edition.  8vo,  cloth net,  $1.60. 

Oilmen's  Sundries,  and  how  to  Make  them:  Being  a  collection 

of  Practical  Recipes  for  Blacking,  Boot  Creams  and 
Polishes,  Harness  Oils,  Pastes  and  Polishes,  Leather 
Dressing  and  Renovators,  Starch  Glazes,  Blues,  Stove 


STANDARD  WORKS  — Continued 

Pastes,  Starch  Tints,  Straw-Hat  Polishes,  Metal  and 
Plate  Polishes,  Furniture  Creams,  Wood  Fillers,  Floor 
Waxes  and  Finishes,  Inks,  Pastes,  Glues,  and  Gums, 
Blackboard  Slating,  Disinfectants,  Cloudy  Ammonia, 
Insecticides,  Hearth-stone  Squares,  etc.  i2mo,  cloth 
net,  $2.00. 

PARRY,  E.  J.,  and  COSTE,  J.  H.    Chemistry  of  Pigments. 

With  tables  and  figures.  8vo,  cloth,  illustrated,  280  pp. 
net,  $4.50. 

PATERSON,    DAVID.     The    Science    of    Color    Mixing:    A 

manual  intended  for  the  use  of  Dyers,  Calico  Printers, 
and  Colour  Chemists.  With  figures,  tables,  and  coloured 
plate.  8vo,  cloth,  illustrated net,  $3.00. 

PULSIFER,  W.  H.    Notes  for  a  History  of  Lead,  and  an 

Inquiry  into  the  Development  of  the  Manufacture  of 
White  Lead  and  Lead  Oxides.  8vo,  cloth.  .  .  .net,  $4.00. 

RANAUD,  PAUL.    Enamels  and  Enamelling:  an  introduction 

to  the  preparation  and  application  of  all  kinds  of  enamels 
for  technical  and  artistic  purposes.  For  enamel  makers, 
workers  in  gold  and  silver,  and  manufacturers  of  objects 
of  art.  Third  German  edition,  translated  by  Charles 
Salter.  With  figures,  diagrams,  and  tables.  8vo,  cloth, 
illustrated  net,  $4.00. 

Recipes  for  the  Color,  Paint,  Varnish,  Oil,  Soap,  and  Dry- 
saltery Trade.  Compiled  by  an  Analytical  Chemist. 
8vo,  347  pp.,  cloth net,  $3.50. 

RIFFAULT:   A  Practical  Treatise  on  the  Manufacture  of 

Colors  for  Painting.  By  MM.  Riffault,  Vergnaud,  and 
Toussaint.  Revised  by  M.  F.  Malepeyre,  and  translated 
from  the  French  by  A.  A.  Fesquet.  8vo,  cloth,  illus- 
trated   net,  $5 .00. 

SCHWEIZER,  V.    Distillation  of  Resins,  Resinate  Lakes  and 

Pigments;  Carbon  Pigments  and  Pigments  for  Type- 
writing Machines,  Manifolders,  etc.  A  description  of 
the  proper  methods  of  distilling  resin-oils,  the  manufacture 
of  resinates,  resin-varnishes,  resin-pigments,  and  enamel 
paints,  the  preparation  of  all  kinds  of  carbon  pigments, 
and  printers'  ink,  lithographic  inks  and  chalks,  and  also 
inks  for  typewriters,  manifolders,  and  rubber  stamps. 
With  tables  and  68  figures  and  diagrams.  8vo,  cloth, 
illustrated.  183  pp net,  $3.50. 

SMITH,  J.  C.  Manufacture  of  Paint.  A  Practical  Hand- 
book for  Paint  Manufacturers,  Merchants,  and  Painters. 
With  60  illustrations  and  one  large  diagram.  8vo,  cloth, 
illustrated  net,  $3.00. 


STANDARD  WORKS —  Concluded 

SPENNRATH,  J.    Protective  Coverings  for  Iron.    A  Chemical 

and  Physical  Examination  of  Paints  commonly  used  for 
the  Protection  of  Iron  against  Corrosion.  Prize  Essay  in 
a  competition  held  under  the  auspices  of  the  Society  for 
the  Advancement  of  the  Industrial  Arts.  8vo,  paper 
net,  $.50. 

STANDAGE,  H.  C.  The  Artists'  Manual  of  Pigments.  Show- 
ing their  Composition,  Conditions  of  Permanency,  Non- 
Permanency,  and  Adulterations ;  effects  in  Combination 
with  each  other  and  with  vehicles;  and  the  most  Reliable 
Tests  of  Purity.  Third  edition.  i2mo,  cloth.  .  .net,  $1.00 

The  Practical  Polish  and  Varnish  Maker.    A  Treatise 

containing  750  Practical  Recipes  and  Formulae  for  the 
Manufacture  of  Polishes,  Lacquers,  Varnishes  and  Japans 
of  all  kinds,  for  Workers  in  Wood  and  Metal,  and  direc- 
tions for  using.  i2mo,  cloth  .  . net,  $2.50. 

SUFFLING,  E.  R.  Treatise  on  the  Art  of  Glass  Painting. 
Prefaced  with  a  Review  of  Ancient  Glass.  With  en- 
gravings and  colored  plates.  8vo,  cloth net,  $3.50. 

TERRY,  G.    Pigments,  Paint,  and  Painting.    A  Practical 

Book  for  Practical  Men.     i2mo,  cloth,  illustrated. 
net,  $3.00. 

WRIGHT,  A.  C.  Simple  Methods  for  Testing  Painters' 
Materials.  8vo,  cloth,  160  pp net,  $2.50. 


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